tag:theconversation.com,2011:/africa/topics/civil-engineering-18947/articlesCivil engineering – The Conversation2024-03-28T18:54:32Ztag:theconversation.com,2011:article/2268342024-03-28T18:54:32Z2024-03-28T18:54:32ZAfter the Baltimore bridge collapse, we need clear-eyed assessments of the risks to key infrastructure<p>Catastrophic collapses of major bridges are thankfully rare. Notable examples in the last couple of decades include the failure of the <a href="https://www.dot.state.mn.us/i35wbridge/collapse.html">I35-W in Minneapolis in August 2007</a>, and the collapse of the <a href="https://theconversation.com/genoa-bridge-collapse-maintaining-these-%20structures-is-a-constant-battle-against-traffic-and-decay-101627">Morandi bridge in Genoa 11 years later</a>. When such events do occur, public attention is understandably focused on the nature of the collapse, which can extend over hundreds of metres in seconds, and its underlying causes. </p>
<p>Whether because of an extreme loading event or an accident, these supposedly rare events in the life of a bridge need to be assessed before they happen, and mitigation measures taken in accordance with the potential consequences. This type of analysis is known as a “risk-based consequence assessment”. The cost of taking additional measures in the near term can prevent major adverse consequences further down the road.</p>
<p>With many bridges being over 50 years old, we often hear that a bridge’s condition may have been compromised by deterioration and increased traffic loads – both in the size and frequency of vehicles. Also, older bridges were designed to standards that have been superseded by new knowledge and technology.</p>
<p>While these factors have helped convince some politicians to increase their infrastructure budgets, including through the <a href="https://www.whitehouse.gov/briefing-room/statements-%20releases/2021/11/06/fact-sheet-the-bipartisan-infrastructure-deal/">Bipartisan Infrastructure Deal</a> in the US, the tendency has been to focus on stronger, more resilient new structures and on higher maintenance for existing structures. Thus, it is easy for politicians to show the money spent has had a positive impact, because it results in an overall reduction in the number of structures classified as obsolete or deficient.</p>
<p>Given the enormous scale of the bridge maintenance problem – the American Road Transportation Builders Association has estimated that <a href="https://theconversation.com/disasters-like-bridge-collapses-put-%20transportation-agencies-emergency-plans-to-the-test-207779">one in three US bridges needs repair</a> – it makes sense to spread available funding widely. However, this approach can have serious shortcomings if it does not set clear priorities based on potential consequences from accidents and failures.</p>
<p>One of the two central pylons of the <a href="https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_(Baltimore)">Francis Scott Key bridge</a> in Baltimore was rammed by a 300m-long container ship at around 1.30am on March 24, leading to progressive collapse of the bridge’s entire <a href="https://en.wikipedia.org/wiki/Truss_bridge">truss</a> within four seconds. </p>
<p>Although the 47-year-old bridge had been <a href="https://www.cbsnews.com/news/francis-scott-key-bridge-baltimore-condition-container-ship-what-we-know-how-collapse-happened/">found to be in a “fair” condition</a> during its most recent inspection in 2008, and was “fully up to code” according to Maryland’s governor after the collapse, experts agreed that a catastrophic collapse <a href="https://www.cbsnews.com/news/francis-scott-key-%20bridge-baltimore-condition-container-ship-what-we-know-how-collapse-happened/">was to be expected</a> given the magnitude of the ship’s impact. Construction workers were on the bridge at the time filling potholes, including the <a href="https://www.bbc.co.uk/news/world-us-canada-68673146">six people who died</a>.</p>
<h2>Direct and indirect consequences</h2>
<p>Bridge collapses due to vessel collisions have happened before and unfortunately will happen again. In a similar incident in 1980, <a href="https://www.structuremag.org/?p=20417">the Sunshine Skyway bridge in Tampa Bay</a>, also a steel truss structure, was hit by a barge, resulting in 35 casualties due to the collapse of over 1,300ft of its span. </p>
<p>Around the world, the American Association of State Highway and Transportation Officials has reported 31 major bridge collapses <a href="https://doi.org/10.1016/j.marstruc.2020.102840">due to vessel collisions</a> between 1960 and 2002, resulting in 342 deaths.</p>
<p>The destruction of the Francis Scott Key Bridge has cut off one of three transport links across the Patapsco river in the busy Baltimore port area. Given its importance as a transport hub, this will have major economic implications that could have been anticipated. </p>
<p>More than 30,000 vehicles that were using the Key Bridge daily now have to seek alternative routes. Significantly, the other two local crossings are via tunnels, which imposes limits on the type of traffic that can cross the river, because the transporting of hazardous materials through tunnels is prohibited.</p>
<p>Shipping traffic into and out of the Baltimore port has been suspended until further notice. Removal of the debris will be a complex operation, and work to ensure all vessel types can navigate the river safely will take time.
Further restrictions will need to be in place when the new bridge is constructed.</p>
<p>There are already signs that supply chains around the world are being affected by the bridge collapse, especially in the car and light truck sector as well as in farm and construction machinery. </p>
<p>The economic consequences of this catastrophic event will be substantial at both city and state level, with potentially wider ripple effects. Early estimates on liability insurance payouts suggest the total cost may <a href="https://www.ft.com/content/17cf3f2e-e64d-4666-b1c2-2723347c2ada">exceed US$1.5 billion (£1.2 billion)</a>. </p>
<p>Judging by what has happened after other bridge collapses, there could be negative impacts on jobs and the local economy: about 14,000 people work in the port itself, and another 140,000 are employed in related services. </p>
<p>Above all, six people lost their lives. But the human cost could have been much worse if the incident had taken place during rush hour. Had the impact occurred with a vessel carrying hazardous materials, the environmental costs could have been dramatic as well.</p>
<h2>What could have been done?</h2>
<p>Given what we know from previous incidents about the severity of ship-bridge collisions and major bridge collapses, decision-makers should have understood the critical importance of this bridge and the consequences of its destruction.</p>
<p>A number of mitigation options were available, including the installation of protection devices around the bridge supports (pylons) in the form of fenders or artificial islands, to deflect a ship or lessen the energy of a collision. </p>
<p>For bridges in general, there are measures that can help on the ship side too, such as requiring the use of tugboats or introducing stricter limits on speeds, depending on the type of cargo and vessel size. It is not clear, however, whether these would have made any difference in the case of the Baltimore bridge collapse.</p>
<p>Above all, by undertaking a risk-based consequence assessment every decade or so, authorities that are responsible for vital infrastructure can help visualise changing risks and prioritise their responses appropriately. In the case of river bridges, ever-increasing ship sizes, speedier turnaround times and higher cargo volumes have all increased the risks – and the costs of a catastrophic collision or collapse.</p><img src="https://counter.theconversation.com/content/226834/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marios Chryssanthopoulos has received funding from UKRI, Network Rail, Highways Agency and the European Commission.</span></em></p>The collapse of the Francis Scott Key bridge is already affecting global supply chains.Marios Chryssanthopoulos, Professor of Structural Systems, University of SurreyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2267952024-03-28T12:51:23Z2024-03-28T12:51:23ZFailure of Francis Scott Key Bridge provides future engineers a chance to learn how to better protect the public<figure><img src="https://images.theconversation.com/files/584884/original/file-20240327-20-ay9lug.jpg?ixlib=rb-1.1.0&rect=37%2C98%2C8206%2C5388&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In this aerial image, the steel frame of the Francis Scott Key Bridge sits on top of a container ship after the bridge collapsed in Baltimore on March 26, 2024. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/in-this-aerial-image-the-steel-frame-of-the-francis-scott-news-photo/2107844094?adppopup=true">Jim Watson for Getty Images</a></span></figcaption></figure><p><em>The cargo ship collision that destroyed the Francis Scott Key Bridge in Baltimore on March 26, 2024, is raising questions about just how much engineers can do to prevent such catastrophes from occurring in the future. Here, <a href="https://scholar.google.com/citations?user=SkGi99AAAAAJ&hl=en&oi=ao">Michael J. Chajes</a>, a professor of civil and environmental engineering at the University of Delaware, discusses how bridge design codes have changed over the years and the challenges of building new structures, and retrofitting existing ones, so they can survive extreme events</em></p>
<h2>How hard is it to design a bridge to withstand the force that took down the Francis Scott Key Bridge?</h2>
<p>Once engineers understand the forces that a structure will be subjected to, they can design a structure to withstand them. That said, we know that each force has a range of magnitudes that can occur. For example, not all trucks on the roadways weigh the same amount, not all earthquakes are of the same magnitude, and not all ships have the same weight. We incorporate this variability in forces into the design.</p>
<p>Even if built to a given set of plans, the final strength of the structure can vary. The materials used have variations in strength. For example, concrete delivered on two successive days will have a sightly different final strength. This variability in the strength of the final structure is also taken into account in the design process to ensure the bridge or building is safe. There’s no way we could build two bridges from the same set of plans and they end up with the exact same strength.</p>
<p>Based on the weight and speed of the ship that hit the Francis Scott Key Bridge, today’s <a href="https://www.fhwa.dot.gov/bridge/pubs/nhi15047.pdf">U.S. bridge design code</a> would call for the bridge to be designed to resist a lateral force of 11,500 tons. This means the bridge has the ability to withstand a lateral hit of that magnitude. That is equivalent to the weight of about 50 loaded Boeing 777s or the weight of the Eiffel Tower. While this is a very large lateral force, structures can be designed to resist such forces. Tall buildings are routinely designed to resist lateral loads of this magnitude that result from wind or earthquakes. However, it is a matter of how much one wants to spend on the structure, and many design goals and constraints need to be balanced against each other.</p>
<h2>What do engineers do to ensure safety in extreme events?</h2>
<p>Our knowledge of how extreme events affect structures is constantly evolving. One area where this is very apparent is <a href="https://theconversation.com/buildings-left-standing-in-turkey-offer-design-guidance-for-future-earthquake-resilient-construction-202089">earthquake engineering</a>. After each earthquake, structural engineers learn what has worked and what has not worked, and then the building and bridge design codes evolve. Infrastructure owners also try to retrofit existing structures that were designed to earlier codes.</p>
<p>Ship collisions and their impact on bridges are a similar area of evolving understanding and improved design codes. There have been over 35 major bridge collapses globally that were caused by <a href="https://conference-service.com/pianc-panama/documents/agenda/data/full_papers/full_paper_46.pdf">ship collisions from 1960 to 2015</a>. Engineers evaluate the failures, and they update the engineering codes so that they better account for the effects of ship collisions. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/JebyNOvJmCM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Cargo ship loses power, crashes into the Francis Scott Key Bridge in Baltimore.</span></figcaption>
</figure>
<h2>How has bridge design evolved since the Baltimore bridge was built?</h2>
<p>The Francis Scott Key Bridge was designed in the early 1970s. Construction started in 1972, and it opened to traffic in 1977. This preceded the <a href="https://www.wesh.com/article/bridge-collapse-florida/60306494">1980 collapse of the Sunshine Skyway</a> in Florida, which was caused by a ship collision, similar to what happened in Baltimore. That bridge collapse led to the initiation of research projects that culminated in the development of a <a href="http://aashto-specifications.blogspot.com/2011/07/aashto-guide-specifications-and.html">U.S. guide specification</a> in 1991 that was updated in 2009.</p>
<p>Based on that guide specification, bridge design codes were changed to include forces due to ship collisions. The design of the Francis Scott Key Bridge would not have been required to consider the effect of ship collisions. The current U.S. bridge design code says that:</p>
<p>“where vessel collision is anticipated, structures should be:</p>
<p>• Designed to resist vessel collision forces and/or</p>
<p>• Adequately protected by fenders, dolphins, berms, islands, or other sacrifice-able devices.”</p>
<p>Other changes since the 1970s are that cargo ships have <a href="https://www.cnn.com/2024/03/27/us/key-bridge-historic-crash-invs/index.html">increased in size and weight</a>. The ship that brought down the Sunshine Skyway in 1980 weighed 35,000 tons, while the ship that collided with the Francis Scott Key Bridge weighed 95,000 tons.</p>
<p>With the increasing weight of cargo ships, the most cost-effective design strategy to prevent collapse of bridges due to vessel collision may well be to protect the bridge piers from the impact. This is done by building a bridge collision protective system, which is often a concrete or rock structure that surrounds the pier and stops the ship from getting to the pier, as is done to protect many of our national monuments.</p>
<p>A pier protection system was installed when the Sunshine Skyway bridge was rebuilt, and it has been used on <a href="https://www.nytimes.com/interactive/2024/03/27/us/key-bridge-barriers-examples.html">numerous other bridges</a>. The same approach is currently being applied by the Delaware River and Bay Authority at a cost of US$93 million to <a href="https://delawarecurrents.org/2024/01/22/delaware-memorial-bridge/">protect the piers of the Delaware Memorial Bridge</a>.</p>
<p>But what about existing bridges like the Francis Scott Key Bridge? Bridge owners have a tremendous challenge finding the financial resources needed to retrofit their bridges to satisfy the latest design codes and to account for the increased impact loads expected due to the heavier and heavier ships. Both things happened here. That is, design codes changed and improved, and loads got much larger. Engineers and infrastructure owners try their best to prioritize where their limited funds can be used to increase structural safety and minimize the chance of structural failure.</p>
<h2>What can universities do?</h2>
<p>The No. 1 job of structural engineers is to protect the public and minimize the risk of structural failures that pose a threat to human life. To do that, engineers must be able to calculate the forces that our structures may be subjected to. This includes cases where a large ship accidentally collides with a bridge, or a large earthquake or hurricane strikes.</p>
<p>In these extreme cases, the structure will almost assuredly sustain damage, but, if at all possible, it should be resilient enough to not collapse. The design codes are continually updated to account for new knowledge, new materials and new design techniques. The reliability of our structures is improving all the time.</p>
<p>Retrofitting structures built to prior codes is an ongoing process, and one that this disaster moves to the forefront. The U.S. has a lot of infrastructure that was designed to old codes, and we have larger trucks crossing our bridges, and larger ships passing beneath them.</p>
<p>Engineers can never reduce the probability of failure to zero, but they can reduce it to the point where failures happen very infrequently and only in cases where numerous unforeseen circumstances combine to make a structure vulnerable to collapse.</p><img src="https://counter.theconversation.com/content/226795/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Michael J. Chajes does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A bridge engineering expert discusses the costs and limitations of building structures to withstand extreme events – and what it takes to prepare the next generation of civil engineers.Michael J. Chajes, Professor of Civil and Environmental Engineering, University of DelawareLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2267852024-03-28T10:23:50Z2024-03-28T10:23:50ZBaltimore Key Bridge: how a domino effect brought it down in seconds<p>The <a href="https://www.bbc.co.uk/news/live/world-us-canada-68663071">collapse of the Francis Scott Key Bridge</a> in Baltimore on 26 March was a shocking and tragic event. Six people remain unaccounted for in the disaster, which saw the world’s third largest continuous truss bridge fall into the Patapsco river.</p>
<p>The cause was Singapore-flagged container ship, the Dali, which veered off course, <a href="https://www.cbsnews.com/news/baltimore-bridge-collapse-ship-what-caused-crash-francis-scott-key-dali/">colliding with one of the bridge’s supports</a>, or piers. As the 300 metre-long vessel slammed into the structure, it triggered what’s known as a <a href="https://www.sciencedirect.com/science/article/pii/S2590123023002177">progressive collapse</a>, where a domino effect leads to the entire structure failing. The bridge, built more than 45 years ago, crashed down into the frigid water at 1:28am eastern standard time (5:28 UTC).</p>
<p>But how could one ship bring down this 366m (1,200 ft) structure within seconds of the collision? </p>
<p>A progressive collapse involves the failure of a single element, like the pier, and results in the sequential failure of other connected components. These can include the metallic truss and the bridge’s deck. This type of collapse can have catastrophic consequences in terms of the risk to human life, as well as to the economy of an area and the local environment. </p>
<p>Although it’s impossible to account for every scenario, bridges can be built with inherent features that enhance their resistance to progressive collapse. Typically, bridges can withstand some degree of damage to a pier or part of the superstructure. The bridge deck can even remain safe for vehicles depending on the circumstances.</p>
<p>However, in the case of the Baltimore bridge collapse, the metallic truss was designed <a href="https://www.washingtonpost.com/local/2024/03/26/francis-scott-key-bridge-history-baltimore/">as one continuous system</a>. The space between each support, or pier, is known as the truss span. The collapse of one of the piers effectively doubled the truss span to the next support. This dramatic increase in span exerted a much larger force on the remaining truss structure. </p>
<p>While continuous truss systems are favoured because they can redistribute weight in the event of damage, in this case, the remaining truss elements couldn’t withstand all that extra force after the pier failed. </p>
<p>This resulted in the complete collapse of the truss section above the damaged
pier. The collapse didn’t stop there, however. Due to the interconnected nature of the trusses, the remaining section was initially pulled upwards. The sudden release of this tension created a powerful dynamic effect, ultimately causing the entire bridge to collapse.</p>
<h2>Rare event</h2>
<p>It’s certainly not unknown for ships to strike bridge supports. On May 9, 1980, <a href="https://www.fox13news.com/news/sunshine-skyway-bridge-francis-scott-key-baltimore-tampa-st-pete-florida-pinellas-hillsborough-collapse-boat-freighter">a strikingly similar event</a> took place when a freighter <a href="https://eu.jacksonville.com/picture-gallery/news/state/2019/05/08/photos-sunshine-skyway-bridge-disaster/809810007/">collided with a support pier of the Sunshine Skyway Bridge</a> in Tampa Bay, Florida. As a result, the bridge failed over a similar distance as the Baltimore collapse.</p>
<p>But while bridge designers are acutely aware of the potential for collisions, these are – at the same time – rather rare events. The impact forces on a support pier are also highly variable. A higher speed or heavier ship will significantly increase the force on the pier. And higher vessel traffic in the water boosts the probability of a collision.</p>
<p>In addition, the current method used in the US for calculating the collision force of a ship is based on <a href="https://www.taylorfrancis.com/chapters/edit/10.1201/b15621-9/vessel-collision-design-bridges-michael-knott-zolan-prucz">research conducted between 1967 and 1976</a>. However, a different method would have been used for the Key Bridge, which opened in 1977. Needless to say, vessels as heavy and fast as the Dali were not a common sight in 1977. </p>
<p>In fact, the collision force under some scenarios is likely to be <a href="https://www.newcivilengineer.com/latest/baltimores-366m-span-steel-truss-bridge-collapses-after-being-struck-by-container-ship-26-03-2024/">well beyond the capacity of bridge piers to withstand</a>. This is why bridges have other systems of protection, such as dolphins – a group of pilings situated in the water near a pier, which serve to deflect a vessel or take the energy out of a collision.</p>
<p>There isn’t any information about the system that was installed when the Key Bridge opened in 1977. And some observers have questioned whether the <a href="https://www.nytimes.com/2024/03/26/us/baltimore-key-bridge-structure-support-pier.html">protective barriers around the Baltimore bridge were sufficient</a>.</p>
<p>Regular structural assessments and retrofits are crucial to ensure a bridge meets current safety standards. Concrete and steel, the primary materials in this bridge, are susceptible to deterioration from factors like corrosion and other environmental conditions. </p>
<p>In general, insufficient maintenance or inadequate retrofits can be contributing factors when bridges collapse. However, it must be said there is no evidence this was a factor in this case – and the Key Bridge <a href="https://web.archive.org/web/20240326081517/https://www.cnn.com/2024/03/26/us/baltimore-key-bridge-collapse-tuesday/index.html">was said to be “up to code”</a> when the disaster occurred. </p>
<p>There will be more detail to come on this dramatic and tragic event. And the findings will surely inform future approaches to the design and protection of bridges across busy waterways.</p><img src="https://counter.theconversation.com/content/226785/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dr Mohamed Shaheen does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We’ll need to learn the lessons from this disaster.Dr Mohamed Shaheen, Lecturer in Structural Engineering, Loughborough UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2267812024-03-28T00:10:00Z2024-03-28T00:10:00ZBridges can be protected from ship collisions – an expert on structures in disasters explains how<figure><img src="https://images.theconversation.com/files/584868/original/file-20240327-24-swqhqh.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C2988%2C1965&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A cargo ship hit the Sunshine Skyway Bridge over Florida's Tampa Bay in 1980, collapsing one span and killing 35 people.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/BridgeCollapses-List/8ccc0211108542268f8c2a39403265d7/photo">AP Photo/Jackie Green</a></span></figcaption></figure><p><em>The MV Dali, a 984-foot, 100,000-ton cargo ship, <a href="https://apnews.com/article/baltimore-bridge-collapse-53169b379820032f832de4016c655d1b">rammed into the Francis Scott Key Bridge</a> when leaving Baltimore harbor on March 26, 2024, causing a portion of the bridge to collapse.</em></p>
<p><em>In an interview, University of Michigan civil engineer <a href="https://scholar.google.com/citations?hl=en&user=764wTXMAAAAJ&view_op=list_works&sortby=pubdate">Sherif El-Tawil</a> explained how often ships collide with bridges, what can be done to protect bridges from collisions, and how a similar disaster in Florida in 1980 – just three years after the Key bridge opened – changed the way bridges are built.</em></p>
<p><strong>This is not the first time a ship has taken out a bridge. What’s the history of ship-bridge collisions?</strong></p>
<p>This is an extremely rare event. To my knowledge, there are about 40 or so recorded events in the past 65 years that involved similar type of damage to a bridge caused by a ship. So they seem to occur on average about once every one and a half to two years around the world. When you consider that there are millions of bridges around the world – and most of them cross waterways – you can imagine how rare this is.</p>
<p>The most influential case was the 1980 <a href="https://www.structuremag.org/?p=20417">Sunshine Skyway Bridge collision</a> in Florida, which prompted the federal government to take action in terms of developing guidelines for designing bridges for ship collision. By the early 1990s the provisions were developed and incorporated into the bridge design code, the AASHTO specifications. The <a href="https://transportation.org/">American Association of State Highway and Transportation Officials</a> produces the design code every bridge in the United States must conform to.</p>
<p><strong>What was different about the Sunshine Skyway Bridge disaster from previous bridge collisions?</strong></p>
<p>There were casualties. The fact that a crash could bring down a bridge, just like in the Baltimore situation, prompted the concern: Can we do something about it? And that something was those specifications that came out and eventually became incorporated in the national design document.</p>
<p>What those specifications say is that you either design the bridge for the impact force that a ship can deliver or you must protect the bridge against that impact force. So you must have a protective system. That’s why I was surprised that this bridge did not have a protective system, some type of barrier, around it. I have not examined the structural plans of this bridge. All I could see is the pictures that were published online, but protective systems would be very visible and recognizable if they were there.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/BvWwKrgdjsI?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Sunshine Skyway Bridge disaster in 1980 prompted improvements in bridge safety.</span></figcaption>
</figure>
<p><strong>What is currently mandated for new bridge construction, and is it sufficient to handle today’s massive cargo ships?</strong></p>
<p>I estimate, based on the published speed and weight of the MV Dali, that the impact force was in the range of 30 million pounds. This is a massive force, and you need a massive structure to withstand that kind of force. But it is doable if you have a huge pier. That might dictate the design of the bridge and what it could look like. Most likely it could not be a <a href="https://www.britannica.com/technology/truss-bridge">truss bridge</a>. It may be a <a href="https://science.howstuffworks.com/engineering/civil/bridge7.htm">cable stay bridge</a> that has a very large tower that is capable of taking that load.</p>
<p>If you cannot design for that load, then you have to consider other alternatives. And that’s what the specifications say. They’re very clear about this. And those alternatives could be to build an island around the pier or a rock wall, or put dolphins – standalone structures set in the riverbed – adjacent to it, or put on fenders that absorb the energy so the ship doesn’t come in so fast. All of these are ways you can mitigate the impact.</p>
<p>Engineers design structures – and bridges are no exception – for a certain probability of failure, because if we didn’t, the cost would be prohibitive. Theoretically, you could build a structure that would never fail, but you’d have to put infinite money into it. For a critical bridge of this type, we would consider an acceptable chance for failure to be <a href="https://conference-service.com/pianc-panama/documents/agenda/data/full_papers/full_paper_46.pdf">1 in 10,000 years</a>.</p>
<p>Based on published information, I tried to compute what the probability of this event would be, and it turns out to be 1 in 100,000 years or so. The ship made a beeline directly to the pier that was vulnerable. It was just shocking to see such a rare event unfold. </p>
<p>The authority of the bridge must have considered protecting it, and the low probability of this occurring must have played a role in whether they would invest or not in protective measures. Because any type of construction in water or on water is very expensive.</p>
<p><strong>Is it feasible to protect older bridges?</strong></p>
<p>I think so. For some of them it might be lower tech like the island idea. And it could use maybe rocks or concrete components that would prevent the ship from reaching the pier at all. </p>
<p>It was a massive ship with a flared bow. The lower part of the ship, which extends beyond the bow, I believe struck the foundation system, but the bow reached the pier. The pier was like an A shape, so the bow snapped one side of the A. The other side could not support the weight of the bridge and so the whole thing collapsed. If somebody kicks your feet from underneath you, you’re just going to fall. That’s exactly what happened.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/JebyNOvJmCM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Video captured the moment the Dali hit a pier of the Francis Scott Key Bridge.</span></figcaption>
</figure>
<p><strong>How many bridges are vulnerable to ship collisions?</strong></p>
<p>I don’t know the number, but I know that bridges that are in this category, that are long span, major bridges like this, are probably less than 0.1% of the bridges in the U.S. And some of them do not necessarily cross waterways, so that’s a subset that is an even lower percentage. So it’s a rare event occurring to a rare kind of bridge. </p>
<p><strong>Are cargo ships getting larger, and is that a consideration for protecting bridges?</strong></p>
<p>I expect so because there is an economy of scale. Bigger ships would be cheaper for transporting goods. But I cannot envision that the designer of this bridge 50 years ago or so would have thought that a ship this size could impact the bridge. I’m sure they would have taken steps to address that. It just didn’t cross their mind.</p>
<p>If this bridge had been designed to the current specifications, I believe it would have survived. There are two reasons a ship would deliver this kind of force: It’s moving too fast or it’s too heavy. And those two factors are taken into consideration in the impact force for which we design. So if we are taking those explicitly into consideration, then a bigger ship, yes, it’s a bigger force, and we would design for that. </p>
<p>But let’s go forward another 50 years and imagine you have a much larger ship that comes into being. At that time, bridges will have been designed for smaller ships, and you have the same problem all over again. It’s hard to predict how big these things will go. You can design for current ships, but as they evolve, it’s hard to predict many years into the future.</p>
<p><strong>Are there other takeaways from this disaster?</strong></p>
<p>The loss of this bridge, beyond the tragic loss of life, is going to be felt for many months if not years. It’s not a straightforward process to replace a bridge of this magnitude, of this span distance. It’s something that will require a lot of planning and a lot of resources to come back again to where we were before.</p><img src="https://counter.theconversation.com/content/226781/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sherif El-Tawil receives funding from the National Science Foundation. </span></em></p>A civil engineer explains why ships taking out bridges is rare, and describes how bridge builders protect the structures from ship collisions.Sherif El-Tawil, Professor of Civil and Environmental Engineering, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2095682023-07-13T12:37:12Z2023-07-13T12:37:12ZClimate change is increasing stress on thousands of aging dams across the US<figure><img src="https://images.theconversation.com/files/536900/original/file-20230711-19-5at0w3.jpg?ixlib=rb-1.1.0&rect=49%2C0%2C5472%2C3604&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Flood damage in Edenville, Mich., after a dam failed on May 19, 2020.</span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/MidwestFlooding/29e7a5cbb920467d9c1b84db02553cd0/photo">AP Photo/Carlos Osorio</a></span></figcaption></figure><p><em>Heavy rainfall in the Northeast on June 9-11, 2023, <a href="https://www.boston.com/news/weather/2023/07/11/montpelier-vermont-floods-possible-dam-breach/">generated widespread flooding</a>, particularly in New York’s Hudson Valley and in Vermont. One major concern was the <a href="https://dec.vermont.gov/water-investment/dam-safety/dec-owned-dams#Wrightsville%20Dam">Wrightsville Dam</a>, built in 1935 on the Winooski River north of Vermont’s capital city, Montpelier. The reservoir behind the dam rose to within 1 foot of the dam’s maximum storage capacity, prompting warnings that water could <a href="https://www.boston.com/news/weather/2023/07/11/montpelier-vermont-floods-possible-dam-breach/">overtop the dam</a> and worsen already-dangerous conditions downstream, or damage the dam.</em></p>
<p><em><a href="https://scholar.google.com/citations?user=1IjEUscAAAAJ&hl=en">Hiba Baroud</a>, associate professor and associate chair in the department of civil and environmental engineering at Vanderbilt University, explains how flooding stresses dams in a changing climate.</em></p>
<h2>How serious is the risk when flooding overtops a dam?</h2>
<p>Dam overtopping can result in erosion, which subsequently could lead to a dam breach or failure and a sudden, uncontrolled release of impounded water.</p>
<p>The risk of dam overtopping results from the combined effect of a hazardous event, such as heavy rainfall, and the vulnerability of the dam. A vulnerable dam could be old, poorly maintained or not have enough <a href="https://www.britannica.com/technology/spillway-engineering">spillway capacity</a> to safely release water from the dam.</p>
<p>A dam’s design can affect its ability to withstand overtopping and resist failure. For example, concrete dams can typically better withstand certain levels of overtopping compared to soil embankment dams. </p>
<p>Overtopping is the leading cause of dam failures in the U.S. It accounts for <a href="https://damsafety.org/dam-failures#The%20Causes%20of%20Dam%20Failures">34% of all dam failures</a>. How long water flows over a dam and the volume of water that flows over it are important factors in determining the likelihood that a dam will fail. </p>
<p>The consequences of a dam overtopping, and possibly failing, depend on several factors, such as the purpose of the dam, its size and its location. If a dam is designed for flood protection and is surrounded by homes, businesses or critical infrastructure, a large uncontrolled release of water could be catastrophic. Dams that are small and located in rural areas may cause less damage if they are overtopped or fail. </p>
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<h2>How old are most US dams?</h2>
<p>There are <a href="https://nid.sec.usace.army.mil/#/">more than 91,000 dams</a> across the U.S., in all 50 states, with diverse designs and purposes. The average dam age is 60 years, and more than 8,000 dams <a href="https://www.nationalgeographic.com/science/article/problem-america-neglected-too-long-deteriorating-dams">are over 90 years old</a>. </p>
<p>Every four years, the <a href="https://www.asce.org/">American Society of Civil Engineers</a> produces a report card for the nation’s infrastructure that assigns grades based on the condition of structures like roads, bridges and dams, and the investments that they need. The most recent report card estimates that 70% of U.S. dams <a href="https://infrastructurereportcard.org/cat-item/dams-infrastructure/">will be more than 50 years old by 2030</a>. </p>
<p>Overall, the report gave U.S. dams a “D” grade and estimated that more than 2,300 <a href="https://www.fema.gov/emergency-managers/risk-management/dam-safety/rehabilitation-high-hazard-potential-dams">high hazard potential dams</a> – those that could cause loss of life or serious property damage if they fail, based on the level of development around them – lacked emergency action plans.</p>
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<figcaption><span class="caption">This video captures the failure of the 90-year-old central spillway of the Lake Dunlap Dam in Seguin, Texas, on May 14, 2019. The collapse led to lawsuits and the creation of a water control district to replace the dam and others like it nearby.</span></figcaption>
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<h2>Are there ways to strengthen older dams against flooding without completely replacing them?</h2>
<p>Decommissioning or replacing dams can be complicated and cost-prohibitive. It also can have cascading effects on the surrounding community, and possibly on other infrastructure. Regularly maintaining and upgrading older dams can be a cost-effective way to strengthen them and make them resilient to natural hazards. </p>
<p>When dams no longer serve the purposes for which they were built, they may be partially breached or <a href="https://theconversation.com/when-dams-cause-more-problems-than-they-solve-removing-them-can-pay-off-for-people-and-nature-137346">entirely removed</a> to restore the river’s natural flow. </p>
<p>The Association of State Dam Safety Officials estimates that it would cost <a href="https://damsafety-prod.s3.amazonaws.com/s3fs-public/files/2023%20ASDSO%20Costs%20of%20Dam%20Rehab%20Report.pdf">US$157.7 billion</a> to rehabilitate all nonfederal dams in the U.S. Of this amount, about one-fifth ($34.1 billion) is for rehabilitating high hazard potential dams. The 2021 <a href="https://www.whitehouse.gov/briefing-room/statements-releases/2021/11/06/fact-sheet-the-bipartisan-infrastructure-deal/">Infrastructure Investment and Jobs Act</a> includes <a href="https://www.congress.gov/bill/117th-congress/house-bill/3684/text">approximately $3 billion</a> for dam safety projects, focusing on rehabilitation, retrofitting and removal.</p>
<h2>Is climate change increasing stress on older dams?</h2>
<p>Climate change is <a href="https://theconversation.com/how-climate-change-intensifies-the-water-cycle-fueling-extreme-rainfall-and-flooding-the-northeast-deluge-was-just-the-latest-209476">increasing the frequency and intensity</a> of natural hazards like storms that threaten dams. And these shifts don’t follow historical trends. Conditions that once were considered extreme will likely be more common in the future. </p>
<p>For example, one recent study on predicting coastal flooding found that in New England, a 100-year flood – that’s an event of a magnitude that now has a 1% chance of occurring in any given year – <a href="https://doi.org/10.1038/s41467-019-11755-z">could become an annual occurrence</a> by the late 2100s. </p>
<p>The fact that the climate is changing also means that extreme events are becoming more extreme. In 2015, a 1,000-year rainfall event in South Carolina resulted in <a href="https://ascelibrary.org/doi/10.1061/9780784480458.024">breaches of 47 dams</a>. </p>
<p>Designing new dams and upgrading existing infrastructure will need to be based on updated design procedures that take into account future climate projections, not just historical hazardous events. While older dams aren’t necessarily unsafe, they were constructed following outdated design standards and construction procedures and for different environmental conditions. That influences the likelihood and consequences of their failure during disasters. </p>
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<figcaption><span class="caption">The near-failure of California’s Oroville Dam in February 2017 led to the evacuation of nearly 190,000 people living downstream. A review cited multiple causes, including design and construction flaws, the bedrock upon which the dam was built and lapses in ongoing inspections.</span></figcaption>
</figure>
<h2>Do you see this event in Vermont as a warning for other communities?</h2>
<p>The disasters that have hit the U.S. in recent years should spur government agencies and communities to prepare and plan for disasters through proactive steps such as developing emergency action plans. </p>
<p>While the number of high hazard potential dams in the U.S. has <a href="https://infrastructurereportcard.org/wp-content/uploads/2020/12/Dams-2021.pdf">more than doubled in the last 20 years</a> as development has moved farther into rural areas, the proportion of these dams with an emergency action plan has also increased. <a href="https://nid.sec.usace.army.mil/#/">It is now at 76%</a>, which is much higher than just a few years ago.</p>
<p>Vulnerable dams and the risk of dam failure cascade through our economy and affect many sectors. Dams serve many purposes: They provide water for drinking and irrigation, generate energy and protect communities from flooding. They are also part of a large navigation network that transports <a href="https://www.iwr.usace.army.mil/Missions/Value-to-the-Nation/Fast-Facts/Inland-Navigation-Fast-Facts/">more than 500 million tons of commodities</a> across the U.S. each year. </p>
<p>As my colleagues and I have shown, it’s important to <a href="https://doi.org/10.1111/risa.12223">understand the direct and indirect costs</a> when critical infrastructure systems like dams fail. This information is crucial for developing strategies that can help the U.S. prepare for future disasters.</p><img src="https://counter.theconversation.com/content/209568/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hiba Baroud receives funding from the National Science Foundation and the Department of Transportation. </span></em></p>More extreme rainfall and frequent storms are raising the risk that floodwaters could spill over dams, or that dams could fail.Hiba Baroud, Associate Professor of Civil and Environmental Engineering, Vanderbilt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2020892023-04-04T12:17:54Z2023-04-04T12:17:54ZBuildings left standing in Turkey offer design guidance for future earthquake-resilient construction<figure><img src="https://images.theconversation.com/files/518309/original/file-20230329-28-3skd0d.jpg?ixlib=rb-1.1.0&rect=11%2C8%2C1905%2C1069&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Turkey's Adana Hospital survived February 2023 earthquakes with no damage because of its seismic isolation system. </span> <span class="attribution"><span class="source">Earthquake Protection Systems, Inc.</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>The Feb. 6, 2023, <a href="https://www.worldbank.org/en/news/press-release/2023/02/27/earthquake-damage-in-turkiye-estimated-to-exceed-34-billion-world-bank-disaster-assessment-report">earthquakes in Turkey and Syria</a> damaged over 100,000 buildings, caused more than 10,000 collapses and killed more than 50,000 people. These earthquakes also put to the test advanced building technologies that can minimize damage and keep buildings functioning after a quake.</p>
<p>Several hospitals built with <a href="https://www.hurriyetdailynews.com/seismic-isolation-devices-prevent-damage-in-four-hospitals-180830">one such technology</a> – called a seismic isolation system – <a href="https://localnewsmatters.org/2023/02/13/vallejo-companys-tech-keeps-turkey-hospital-operational-after-devastating-earthquakes/">survived the earthquakes</a> with almost no harm, according to local news reports, even while surrounding buildings sustained heavy damage. </p>
<p>Adana City Hospital was built to record both ground shaking and the building’s response. Thanks to its seismic isolation system, the building saw a 75% <a href="https://www.earthquakeprotection.com/">reduction in shaking</a>, according to the company that designed the isolation system, compared with neighboring structures. This system allowed the building to stay up and running after the earthquake.</p>
<p>Engineers aren’t surprised that the hospitals with seismic isolation systems survived with minimal damage, but through <a href="https://scholar.google.com/citations?user=VdoAeqAAAAAJ&hl=en">my work as a civil engineer</a>, I’ve been hearing people in Turkey and abroad ask why more buildings don’t use these smarter engineering technologies.</p>
<p>A year after the 1999 İzmit earthquake in Turkey killed over 17,000 people, I moved to Istanbul for a bachelor’s in civil engineering. I moved to the U.S. for my graduate studies in 2005, and since then, I have been working on advanced technologies and materials that can ensure rapid recovery and reoccupation of buildings <a href="https://engineering.virginia.edu/rail">after a strong earthquake</a>.</p>
<p>Although we’ve seen the effectiveness of seismic protection technologies during past major earthquakes, these technologies have been installed in only a tiny fraction of the places where they could potentially be useful.</p>
<h2>Earthquake-resilient building technology</h2>
<p>Engineers can control how structures respond to earthquakes in several ways.</p>
<p><a href="https://permanent.fdlp.gov/gpo15358/fema_p_749.pdf">Traditional approaches</a> rely on having certain components of the building, like columns or beams, absorb the earthquake’s energy. However, this method can lead to damage accumulating in these structural features that <a href="https://www.enr.com/articles/3447-engineers-surprised-by-damage-to-modern-buildings-in-christchurch">may render the building uninhabitable</a>.</p>
<p><a href="https://www.sciencelearn.org.nz/resources/1022-base-isolation-and-seismic-dampers">Earthquake-resilient systems</a> such as seismic isolation devices and seismic dampers minimize the seismic energy that goes into these columns or beams by either absorbing it or diverting it. As a result, the building experiences less motion and damage and is more likely to <a href="https://doi.org/10.3389/fbuil.2020.00126">remain functional</a> after an earthquake.</p>
<p><a href="https://www.hurriyetdailynews.com/seismic-isolation-devices-prevent-damage-in-four-hospitals-180830">Seismic isolation systems</a> prevent seismic energy from entering buildings in the first place by using devices made from rubber or steel plates coated with a friction-generating material that slide over one another to minimize an earthquake’s impact. These isolation devices are installed between the building’s foundation and the building itself. Alternatively, seismic dampers, installed in each story of a building, absorb earthquake energy the way shock absorbers work in a car and convert it into heat energy to <a href="https://buildcivil.wordpress.com/2013/11/25/passive-energy-dissipation-devices/">minimize damage</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/518267/original/file-20230329-2631-bzokl7.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An illustration showing two side-by-side structures, the left with arrows denoting side-to-side motion. The right has small blocks at the building's foundation which absorb seismic energy and prevent motion." src="https://images.theconversation.com/files/518267/original/file-20230329-2631-bzokl7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/518267/original/file-20230329-2631-bzokl7.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=391&fit=crop&dpr=1 600w, https://images.theconversation.com/files/518267/original/file-20230329-2631-bzokl7.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=391&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/518267/original/file-20230329-2631-bzokl7.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=391&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/518267/original/file-20230329-2631-bzokl7.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=491&fit=crop&dpr=1 754w, https://images.theconversation.com/files/518267/original/file-20230329-2631-bzokl7.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=491&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/518267/original/file-20230329-2631-bzokl7.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=491&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The left shows a building without seismic isolation, while the right image shows a building with a seismic isolation system, which minimizes how much damage the building sustains during an earthquake. The red lines denote how much motion the building could experience during an earthquake.</span>
<span class="attribution"><span class="source">Ozbulut Lab</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Both seismic isolation systems and seismic dampers can help a building achieve “<a href="https://www.nibs.org/blog/resilience-2021-importance-seismic-functional-recovery-and-community-resilience-built">functional recovery</a>” – a performance objective whereby buildings are constructed to prevent damage and enable reoccupancy. Designing such buildings will not only save people and buildings but also keep the earthquakes from collapsing communities and economies. </p>
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<p>While functional recovery is an emerging idea for building earthquake-resilient structures, global modern building codes stipulate that, at a minimum, structures must have measures in place to keep the building from collapsing – called the <a href="https://www.fema.gov/node/seismic-building-code-provisions-new-buildings-create-safer-communities">life safety objective</a>. Buildings following a life safety objective are engineered to sustain damage in a controlled way, to keep the building standing and protect those inside.</p>
<p>While these buildings likely won’t collapse, they may not be safe to use after a quake. While this is not the same as functional recovery, if more buildings had been built to a life safety threshold in Turkey and Syria, thousands of lives could have been saved.</p>
<h2>The case in Turkey</h2>
<p>Much of the damage in Turkey occurred in nonductile concrete buildings constructed under a pre-1998 Turkish building code. Ductile concrete building elements, required by newer building codes, are more flexible, thanks to steel reinforcing bars at critical locations. They can <a href="https://www.concreteconstruction.net/how-to/construction/earthquakes-and-reinforced-concrete_o">accommodate the building motions</a> induced by earthquakes. The older nonductile buildings also tended to have poorly arranged steel reinforcements, leaving them vulnerable to the sudden collapse of building columns.</p>
<figure>
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<figcaption><span class="caption">This video, from The Associated Press, shows some of the buildings that collapsed in the aftermath of the Turkey earthquakes.</span></figcaption>
</figure>
<p>Similarly, many so-called soft-story buildings were damaged during these earthquakes. A soft story is a level that is significantly more vulnerable to lateral earthquake forces than the other stories in a multistory building. The first floor of these buildings – commonly used for commercial purposes like retail, garage or office space – tend to have more open areas and fewer structural components, like beams and columns, making them vulnerable to collapse.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517774/original/file-20230327-14-2qrw3m.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A partially collapsed tan building, leaning to the right side." src="https://images.theconversation.com/files/517774/original/file-20230327-14-2qrw3m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517774/original/file-20230327-14-2qrw3m.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=891&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517774/original/file-20230327-14-2qrw3m.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=891&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517774/original/file-20230327-14-2qrw3m.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=891&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517774/original/file-20230327-14-2qrw3m.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1120&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517774/original/file-20230327-14-2qrw3m.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1120&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517774/original/file-20230327-14-2qrw3m.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1120&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">An example of a soft-story building, where the first story collapsed, leaving the rest of the floors relatively stable.</span>
<span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/TurkeySyriaEarthquake/48bbd617383140649e53dcb6fa509f79/photo?Query=turkey%20earthquake%20building%20collapse&mediaType=photo&sortBy=&dateRange=Anytime&totalCount=1042&currentItemNo=261">AP Photo/Emrah Gurel</a></span>
</figcaption>
</figure>
<p>These types of buildings are found all over the world, including in highly populated, seismically at-risk areas like <a href="https://www.voanews.com/a/turkey-s-deadly-quake-renews-alarm-for-istanbul-/6968544.html#:%7E:text=Seismologists%20warn%20that%20a%20massive,to%2020%20million%20%E2%80%94%20by%202030.">Istanbul</a>, <a href="https://www.sfchronicle.com/sf/article/earthquake-building-risk-safety-17782287.php">San Francisco</a>, Los Angeles and Vancouver — all located near active fault lines.</p>
<p>Buildings designed under old codes can be strengthened to meet a life safety performance threshold. However, these upgrades can cost lots of money, and enforcing these upgrades, especially for private buildings, requires well-planned policies.</p>
<h2>Learning lessons</h2>
<p>While buildings designed for a life safety objective can protect thousands of lives, the February 2011 Christchurch earthquake in New Zealand revealed the limitations of modern seismic codes centered solely on this design goal. The damage to buildings designed under a life safety goal was so extensive that thousands had to be <a href="https://www.nist.gov/news-events/news/2021/01/new-report-charts-path-toward-superior-earthquake-recovery">demolished after the quake</a>. </p>
<p>It was this earthquake that led engineers to focus on “functional recovery” and to implement seismic protective technologies more widely. The <a href="https://thehill.com/opinion/energy-environment/504572-smarter-engineering-could-help-recovery-from-major-disasters/">additional cost</a> of such <a href="https://www.nytimes.com/1988/10/30/realestate/base-isolation-taking-the-shock-out-of-quakes.html">seismic protection technologies</a> is typically <a href="https://www.usrc.org/usrc-media-portfolio/#Papers">less than 5%</a> of the initial construction costs and pales in comparison to the cost of the social and economic disruptions caused by a major earthquake. In addition, securing lower insurance premiums may recoup most of these initial costs.</p>
<p>Total economic losses after the Christchurch earthquake was estimated at <a href="https://www.bloomberg.com/news/articles/2013-04-28/christchurch-quake-rebuild-soars-33-to-nz-40-billion-key-says#xj4y7vzkg">US$32 billion</a>, not accounting for inflation, of which $24 billion was construction costs. The cost of the recent earthquakes in Turkey is estimated to be more than <a href="https://www.reuters.com/world/middle-east/earthquake-could-cost-turkey-up-84-bln-business-group-2023-02-13/">$84 billion</a> and still counting.</p>
<p>The earthquakes in Turkey have shown that seismic protection technologies work. To avoid high economic and social consequences, local authorities can update the provisions and codes for designing new buildings to enable post-earthquake reoccupancy and functional recovery. Additionally, policies, financial incentives and tax benefits that promote enhanced building design could improve seismic safety on a larger scale.</p><img src="https://counter.theconversation.com/content/202089/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Osman Ozbulut receives funding from NSF. </span></em></p>February earthquakes wreaked havoc across Turkey and Syria, killing tens of thousands of people. An engineer originally from Turkey describes what kept some buildings functional while others collapsed.Osman Ozbulut, Associate Professor of Civil Engineering, University of VirginiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1879612022-08-02T12:58:26Z2022-08-02T12:58:26ZWhat is a flash flood? A civil engineer explains<figure><img src="https://images.theconversation.com/files/536602/original/file-20230710-17-awc1e1.jpg?ixlib=rb-1.1.0&rect=0%2C6%2C4460%2C2962&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Pickup trucks creep through flood waters in Richland, Miss., following a morning of torrential rains in August 2022. </span> <span class="attribution"><a class="source" href="https://newsroom.ap.org/detail/FlashFloodingMississippi/577c058ef3e845479fbeacf1b44625ca/photo">AP Photo/Rogelio V. Solis</a></span></figcaption></figure><p>Flash flooding is a specific type of flooding that occurs in a short time frame after a precipitation event – <a href="https://www.weather.gov/mrx/flood_and_flash">generally less than six hours</a>. It often is caused by heavy or excessive rainfall and happens in areas near rivers or lakes, but it also can happen in places with no water bodies nearby.</p>
<p>Flash floods happen in both rural and urban areas, as in July 2023 in <a href="https://nypost.com/2023/07/09/water-rescues-underway-after-flash-flooding-wallops-parts-of-northeast-with-53-million-at-risk-through-monday/">New York state’s Hudson Valley</a>. When more rainfall lands in an area than the ground can absorb, or it falls in areas with a lot of impervious surfaces like concrete and asphalt that prevent the ground from absorbing the precipitation, the water has few places to go and can rise very quickly.</p>
<p>If an area has had recent rainfall, the soil may be saturated to capacity and unable to absorb any more water. Flooding can also occur after a drought, when soil is too dry and hardened to absorb the precipitation. Flash floods are <a href="https://www.blm.gov/flash-floods-tread-safely#:%7E:text=Flash%20floods%20can%20happen%20at,fast%2Dmoving%2C%20high%20water.">common in desert landscapes</a> after heavy rainfalls and in areas with shallow soil depths above solid bedrock that limits the soil’s ability to absorb rain.</p>
<p>Since water runs downhill, rainfall will seek the lowest point in a potential pathway. In urban areas, that’s often streets, parking lots and basements in low-lying zones. In rural areas with steep terrain, such as Appalachia, flash flooding can turn creeks and rivers into raging torrents. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/GBPnZXIp94g?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Heavy rain generated flash flooding in the lower Hudson River Valley on July 9, 2023.</span></figcaption>
</figure>
<p>Flash floods often catch people by surprise, even though weather forecasters and emergency personnel try to warn and prepare communities. These events can <a href="https://www.youtube.com/watch?v=n93QKa_LgUg">wash away cars</a> and even <a href="https://www.nytimes.com/live/2022/07/29/us/kentucky-flooding-west-virginia">move buildings off their foundations</a>. </p>
<p>The best way to stay safe in a flash flood is to be aware of the danger and be ready to respond. Low-lying areas are at risk of flooding, whether it happens slowly or quickly and whether it’s an urban or rural setting. </p>
<p>It’s critical to know where to get up-to-date weather information for your area. And if you’re outdoors and encounter flooded spots, such as water-covered roadways, it is always safer to wait for the water to recede or turn back and find a safer route. Don’t attempt to cross it. Flood waters can be much faster and stronger than they appear – and therefore more dangerous.</p>
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<h2>Building for a wetter future</h2>
<p>Engineers design stormwater control systems to limit the damage that rainfall can do. Culverts transfer water and help <a href="https://civiltoday.com/construction/bridge/115-what-is-a-culvert-definition-materials-purpose-location-installation">control where it flows</a>, often directing it underneath roads and railways so that people and goods can continue to move safely. Stormwater containment ponds and <a href="https://www.asce.org/communities/institutes-and-technical-groups/environmental-and-water-resources-institute/design-of-stormwater-control-methods">detention basins</a> hold water for release at a later time after flooding has ceased. </p>
<p>Many cities also are using <a href="https://www1.nyc.gov/assets/dep/downloads/pdf/water/stormwater/green-infrastructure/gi-annual-report-2020.pdf">green infrastructure systems</a>, such as rain gardens, green roofs and permeable pavement, to <a href="https://www.epa.gov/smartgrowth/city-green-innovative-green-infrastructure-solutions-downtowns-and-infill-locations">reduce flash flooding</a>. <a href="https://www.epa.gov/wetlands/incorporating-wetland-restoration-and-protection-planning-documents">Restoring wetlands</a> along rivers and streams helps mitigate flooding as well. </p>
<p>Often the design standards and rules that we use to engineer these features are based on historic rainfall data for the location where we’re working. Engineers use that information to calculate how large a culvert, pond or other structure might need to be. We always build in some excess capacity to handle unusually large floods. </p>
<p>Now, however, many parts of the U.S. are experiencing more intense storm events that drop significant amounts of rainfall on an area in a very short time period. On July 9, 2023, West Point, New York, received more than 7.5 inches of rain in 6 hours – a scale that statistically would be expected to occur there <a href="https://www.cnn.com/2023/07/10/weather/northeast-storms-flooding-excessive-rainfall/index.html">once in 1,000 years</a>. </p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1678232145393774593"}"></div></p>
<p>With climate change, we expect this trend to continue, which means that planners and engineers will need to reconsider how to design and manage infrastructure in the future. But it’s hard to predict how frequent or intense future storm events will be at a given location. And while it’s extremely likely that there will be more intense storm events based upon climate projections, designing and building for the worst-case situation is not cost effective when there are other competing demands for funding.</p>
<p>Right now, engineers, hydrologists and others are working to understand how best to plan for the future, including modeling flood events and development trends, so that we can help communities make themselves more resilient. That will require more, updated data and design standards that better adapt to anticipated future conditions.</p>
<p><em>This article has been updated to reflect flash flooding in New York in July 2023.</em></p><img src="https://counter.theconversation.com/content/187961/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Janey Camp is a member of the American Society of Civil Engineers Committee for America’s Infrastructure, the American Association of State Floodplain Managers and the Tennessee Association of State Floodplain Managers.</span></em></p>Flash flooding can happen in both urban and rural areas, with deadly results in either setting.Janey Camp, Research Professor of Civil and Environmental Engineering, Vanderbilt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1613972021-06-02T12:26:03Z2021-06-02T12:26:03ZSick of dangerous city traffic? Remove left turns<figure><img src="https://images.theconversation.com/files/403824/original/file-20210601-15-ogp78e.jpg?ixlib=rb-1.1.0&rect=779%2C136%2C3734%2C2578&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Left turns are dangerous and cause a lot of unnecessary traffic. </span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/red-traffic-light-over-street-intersection-royalty-free-image/1149332178?adppopup=true">Chris Jongkind/Moment via Getty Images</a></span></figcaption></figure><p>To reduce travel times, fuel consumption and carbon emissions, in 2004, UPS changed delivery routes to <a href="https://priceonomics.com/why-ups-trucks-dont-turn-left/">minimize the left-hand turns</a> drivers made. Although this seems like a rather modest change, the results are anything but: UPS claims that per year, eliminating left turns – specifically the time drivers sit waiting to cut across traffic – saves <a href="https://theconversation.com/why-ups-drivers-dont-turn-left-and-you-probably-shouldnt-either-71432">10 million gallons of fuel, 20,000 tons of carbon emissions</a> and allows them to deliver 350,000 additional packages.</p>
<p>If it works so well for UPS, should cities seek to eliminate left-hand turns at intersections too? My research suggests the answer is a resounding yes. </p>
<p>As a <a href="https://sites.psu.edu/gayah/">transportation engineering professor</a> at Penn State, <a href="https://scholar.google.com/citations?user=gIKMKzgAAAAJ&hl=en&oi=ao">I have studied</a> traffic flow on urban streets and transportation safety for nearly a decade. Part of my work focuses on how city streets should be organized and managed. It turns out, restricting left turns at intersections with traffic signals <a href="https://doi.org/10.3141/2301-09">lets traffic move more efficiently</a> and <a href="https://nacto.org/docs/usdg/development_left_turn_operations_guidelines_yu.pdf">is safer for the public</a>. In a recent paper, my research team and I developed a way to determine <a href="https://doi.org/10.1177/03611981211011647">which intersections should restrict left turns to improve traffic</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/403825/original/file-20210601-13-rje2g7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two cars in an intersection after colliding." src="https://images.theconversation.com/files/403825/original/file-20210601-13-rje2g7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/403825/original/file-20210601-13-rje2g7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/403825/original/file-20210601-13-rje2g7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/403825/original/file-20210601-13-rje2g7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/403825/original/file-20210601-13-rje2g7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/403825/original/file-20210601-13-rje2g7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/403825/original/file-20210601-13-rje2g7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Left turns are responsible for 61% of all car accidents at intersections.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/car-accident-royalty-free-image/479044140?adppopup=true">studiodr/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>Why are left-hand turns so bad?</h2>
<p>Intersections are dangerous because they are where cars, often moving very fast and in different directions, must cross paths. <a href="https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/811366#:%7E:text=Based%20on%20the%20Fatality%20Analysis,20081%20were%20intersection%2Drelated%20crashes.">Approximately 40% of all crashes occur at intersections</a>, including 50% of crashes involving serious injuries and 20% of those involving fatalities. Traffic signals make things safer by giving vehicles instructions on when they can move. If left turns did not exist, the instructions could be very simple: For example, a north-south direction could move while the east-west direction was stopped and vice versa. When drivers make left turns, they must cross oncoming traffic, which makes intersections much more complicated.</p>
<p>One way to accommodate left turns is to have vehicles wait until a gap appears in oncoming traffic. However, this can be dangerous as it relies entirely on the driver to make the left turn safely. And everyone knows how frustrating it is to be stuck behind a car waiting to make a left turn on a busy road.</p>
<p>Another way to allow left-hand turns is to stop oncoming traffic and give cars turning left their own green arrow. This is much safer, but it shuts down the entire intersection to let left-turning vehicles go, which slows traffic considerably.</p>
<p>In either case, left turns are dangerous. Approximately 61% of all crashes that occur at intersections <a href="https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/811366#:%7E:text=Based%20on%20the%20Fatality%20Analysis,20081%20were%20intersection%2Drelated%20crashes">involve a left-hand turn</a>. </p>
<h2>How would eliminating left turns improve traffic?</h2>
<p>Traffic researchers have proposed a variety of <a href="https://safety.fhwa.dot.gov/intersection/rltci/">innovative signal strategies</a> and <a href="https://www.fhwa.dot.gov/publications/research/safety/09060/09060.pdf">complex intersection configurations</a> to make left turns safer and more efficient. But a simpler solution might be the best: Restrict left-hand turns at intersections.</p>
<p>Some cities have already started limiting left turns to improve safety and traffic flow. <a href="https://www.sfexaminer.com/news/city-to-remove-left-turn-on-van-ness-leaving-only-two-lefts-on-corridor/">San Francisco</a>; <a href="https://archive.sltrib.com/article.php?id=52896856&itype=CMSID">Salt Lake City</a>; <a href="https://www.al.com/spotnews/2013/09/michigan_left_u-turn_along_us.html">Birmingham</a>, Alabama; <a href="https://lifeinbrunswickcounty.com/the-michigan-left-superstreet-heading-eastbound-a-midwestern-traffic-pattern-takes-a-detour-to-north-brunswick-county/">Wilmington</a>, Delaware; <a href="https://tucson.com/news/local/govt-and-politics/little-love-for-michigan-left/article_d0dc7114-c46d-5f52-9d65-90723c50de19.html">Tuscon</a>, Arizona; <a href="https://www.michiganradio.org/post/revisiting-origin-michigan-left">numerous locations in Michigan</a>; and dozens of other cities in the U.S. and around the world all limit left turns in some way. It’s typically done at isolated locations to solve specific traffic and safety problems.</p>
<p>Of course, there is a downside. Eliminating left turns would require some vehicles to travel longer distances. For example, if you wanted to turn left off a busy street to get to your house, you might instead have to take three consecutive right turns. However, research I <a href="https://doi.org/10.3141/2301-09">published in 2012 using mathematical models</a> and <a href="https://doi.org/10.1080/21680566.2017.1337528">in 2017 using traffic simulations</a> showed that eliminating left turns on grid-like street networks would, on average, require people to drive only one additional block. This would be more than offset by the smoother traffic flow.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/403826/original/file-20210601-663-1gnx1tg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An aerial view of an intersection with cars making a left turn." src="https://images.theconversation.com/files/403826/original/file-20210601-663-1gnx1tg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/403826/original/file-20210601-663-1gnx1tg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/403826/original/file-20210601-663-1gnx1tg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/403826/original/file-20210601-663-1gnx1tg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/403826/original/file-20210601-663-1gnx1tg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/403826/original/file-20210601-663-1gnx1tg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/403826/original/file-20210601-663-1gnx1tg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Cities could limit left turns in busy city centers while allowing them in less busy areas.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/aerial-view-of-city-traffic-royalty-free-image/119544689?adppopup=true">Jeppe Wikstrom via Getty Images</a></span>
</figcaption>
</figure>
<h2>Which left turns need to go?</h2>
<p>Getting rid of left turns would be difficult to implement across an entire city – and at some intersections, left turns don’t cause problems. But if a city did want to remove left turns from some intersections, how should it choose which ones? To answer this question, my research team and I recently developed algorithms that use traffic simulations of a city to <a href="https://doi.org/10.1177/03611981211011647">identify where restricting left turns will improve safety and traffic flow the most</a>. </p>
<p>[<em>Get the best of The Conversation, every weekend.</em> <a href="https://theconversation.com/us/newsletters/weekly-highlights-61?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=weeklybest">Sign up for our weekly newsletter</a>.]</p>
<p>The exact answer for each city depends on how streets are laid out, where vehicles are coming from and going to and how much traffic is on the street during the busiest times. But, according to our models, there is a general theme: Left-turn restrictions are more effective at busier intersections in the centers of towns or cities than at less busy intersections farther from the town center.</p>
<p>This is because the busier the intersection, the more people will benefit from smoother traffic flow. These central intersections also tend to have alternative routes available that minimize any additional distance traveled due to the restrictions. Lastly, fewer cars tend to turn left at these central intersections to begin with so the negative impact of removing left turns is relatively small.</p>
<p>So the next time you are sitting stuck in traffic behind someone waiting to make a left turn, know that your frustration is justified. There is a better way. In this case, the answer is simple – get rid of the left turn.</p><img src="https://counter.theconversation.com/content/161397/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Vikash V. Gayah receives funding from the National Science Foundation and National Cooperative Highway Research Program. </span></em></p>Left turns are dangerous and slow down traffic. One solution? Get rid of them. New research shows that limiting left turns at busy intersections would improve safety and reduce frustrating backups.Vikash V. Gayah, Associate Professor of Civil Engineering, Penn StateLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1538692021-03-30T11:37:05Z2021-03-30T11:37:05ZHow to make sure Biden’s infrastructure plan can hold up to climate change – and save money<figure><img src="https://images.theconversation.com/files/392343/original/file-20210329-19-o9jwt2.jpg?ixlib=rb-1.1.0&rect=56%2C62%2C1928%2C1263&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In the Netherlands, some flood control systems are designed to adapt to future climate change.
</span> <span class="attribution"><a class="source" href="https://www.rijkswaterstaat.nl/en/water/water-safety/delta-works">Dutch Ministry of Infrastructure and Water Management</a></span></figcaption></figure><p>The Biden administration is proposing a <a href="https://www.nytimes.com/2021/03/22/business/biden-infrastructure-spending.html">massive infrastructure plan</a> to replace the nation’s crumbling bridges, roads and other critical structures. But to make those investments pay off, the U.S. will need designs that can endure the changing climate.</p>
<p>Most U.S. infrastructure is designed to stand for decades, including through what engineers expect to be rare storms and floods.</p>
<p>However, extreme storms that were considered rare a few decades years ago are already becoming more common. <a href="https://www.weather.gov/hgx/hurricaneharvey">Hurricane Harvey</a> in 2017 was the Houston area’s <a href="https://www.washingtonpost.com/news/wonk/wp/2017/08/29/houston-is-experiencing-its-third-500-year-flood-in-3-years-how-is-that-possible/">third “500-year flood”</a> in three years, and it was followed by two more major flooding events.</p>
<p>Building infrastructure today that will be strong enough to manage the extreme scenarios the nation might see a century from now can be expensive. But what if infrastructure were instead designed to meet shorter-term needs and also be easily adapted later for the future climate?</p>
<p>I’m a <a href="https://cee.engin.umich.edu/people/jeremy-bricker/">hydraulic and coastal engineer</a> who has been working on infrastructure design in the Netherlands, where dams and storm surge barriers are being designed to be adaptable. The methods there hold lessons for the U.S. as it prepares for a wave of new construction.</p>
<h2>The problem with building for 100-year floods</h2>
<p>Bridges in the U.S. are typically designed to allow the unimpeded passage of floods that have a <a href="https://doi.org/10.1061/(ASCE)IS.1943-555X.0000354">1-in-100 chance</a> of happening each year. Similarly, a dam spillway might be built to handle a 10,000-year flood, and stormwater drains for two-year rainfall events. </p>
<p>These “return periods” are traditionally calculated <a href="https://water.usgs.gov/osw/bulletin17b/dl_flow.pdf">using a method</a> based on historical statistics that assume the climate doesn’t change much. </p>
<figure class="align-center ">
<img alt="Water is released from the dam" src="https://images.theconversation.com/files/392374/original/file-20210329-13-8v9qnj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/392374/original/file-20210329-13-8v9qnj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/392374/original/file-20210329-13-8v9qnj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/392374/original/file-20210329-13-8v9qnj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/392374/original/file-20210329-13-8v9qnj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/392374/original/file-20210329-13-8v9qnj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/392374/original/file-20210329-13-8v9qnj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">During Hurricane Harvey’s extreme rainfall, water was released from Houston’s Barker Reservoir to protect its dam and upstream neighborhoods. Downstream neighborhoods flooded as a result.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/the-barker-reservoir-and-buffalo-bayou-dam-are-shown-august-news-photo/841958498?adppopup=true">Win McNamee/Getty Images</a></span>
</figcaption>
</figure>
<p>In a warming climate with more extreme rainfall, worsening droughts and rising sea levels, these historical statistics can <a href="http://ascelibrary.org/doi/abs/10.1061/(ASCE)IS.1943-555X.0000354">underestimate the intensity</a> <a href="https://doi.org/10.1038/nclimate1911">of future floods</a>. That puts critical infrastructure, homes and lives in danger.</p>
<h2>Putting adaptive design to work</h2>
<p>The Dutch are masters of flood control. When <a href="https://www.netherlands-tourism.com/netherlands-sea-level/">about a third</a> of a country sits below sea level, it becomes a necessity. U.S. engineers have been <a href="https://www.texastribune.org/2019/07/15/can-masters-flood-help-texas-protect-its-coast-hurricanes/">turning to them</a> for advice in recent years as understanding of climate change and its impact on storms and sea level rise increases. </p>
<p>The Netherlands’ innovative designs, like the giant gates of the <a href="https://youtu.be/wetmgwicbXs">Maeslant flood defense</a>, are getting noticed, but equally important is how the Dutch use adaptive designs to prepare for the future and keep costs under control.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/wetmgwicbXs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Maeslantkering protects The Hague, Rotterdam and other cities from high tides from the North Sea.</span></figcaption>
</figure>
<p>To see adaptive design at work, look at the <a href="https://deafsluitdijk.nl/">renovation underway of the Afsluitdijk</a>, a 20-mile-long dam that protects Amsterdam’s port from storm surges on the North Sea.</p>
<p>When the dam was completed in 1932, it drained river water to the sea by gravity at low tide. However, sea level rise, combined with the need to keep the water level in Amsterdam’s port low to protect the city, are making drainage by gravity alone increasingly ineffective.</p>
<p>To update the dam, the Dutch have built pump stations for draining water into the North Sea. Importantly, the new design reserves enough land to expand the existing pump stations or build new ones <a href="https://www.ipcc.ch/srocc/">when future storms and sea level rise make it necessary</a>. </p>
<figure class="align-center ">
<img alt="Aerial view of the dam" src="https://images.theconversation.com/files/392338/original/file-20210329-15-lj1okq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/392338/original/file-20210329-15-lj1okq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=378&fit=crop&dpr=1 600w, https://images.theconversation.com/files/392338/original/file-20210329-15-lj1okq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=378&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/392338/original/file-20210329-15-lj1okq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=378&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/392338/original/file-20210329-15-lj1okq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=475&fit=crop&dpr=1 754w, https://images.theconversation.com/files/392338/original/file-20210329-15-lj1okq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=475&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/392338/original/file-20210329-15-lj1okq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=475&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The sluice gates in the center of the image allow water to pass through the Afsluitdijk between the IJsselmeer and the North Sea. The lock to the left of the sluice gates raises and lowers boats.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/mdvanleeuwen/10127900265">Marcus van Leeuwen/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Lessons as the U.S. plans new coastal protections</h2>
<p>Several U.S. cities, including <a href="https://www.scientificamerican.com/article/a-proposed-storm-surge-barrier-could-protect-texas-from-storms-like-laura/">Houston</a>, <a href="https://www.nytimes.com/2020/01/17/nyregion/sea-wall-nyc.html">New York</a> and <a href="https://doi.org/10.1007/s10584-020-02781-8">Boston</a>, are now considering hurricane defense systems, and the future protection they will <a href="https://doi.org/10.5194/nhess-20-2397-2020">actually need</a> <a href="https://www.ipcc.ch/report/ar5/wg1/">to prevent flooding</a> is unknown at this point. </p>
<p>By using adaptive design, they could include room for expanding those defenses as the climate changes. </p>
<p>That might mean building earthen dams and levees wide enough to allow for raising them when necessary, and reserving land for widening and heightening of coastal dunes that form part of the system and for adding pump infrastructure. </p>
<p>Crucially, movable storm surge barriers, which typically make up a short section of a barrier system, offer protection only from sporadic hurricanes and not from long-term sea level rise. The movable barriers may eventually need to be replaced with a dam, shipping lock and drainage pumps – that, too, can be planned for. </p>
<figure class="align-center ">
<img alt="Map of South Boston showing flood risk" src="https://images.theconversation.com/files/392094/original/file-20210328-23-1yiue3h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/392094/original/file-20210328-23-1yiue3h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=333&fit=crop&dpr=1 600w, https://images.theconversation.com/files/392094/original/file-20210328-23-1yiue3h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=333&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/392094/original/file-20210328-23-1yiue3h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=333&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/392094/original/file-20210328-23-1yiue3h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=419&fit=crop&dpr=1 754w, https://images.theconversation.com/files/392094/original/file-20210328-23-1yiue3h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=419&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/392094/original/file-20210328-23-1yiue3h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=419&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">This map of Boston shows future flood risks if no protective measures are taken.</span>
<span class="attribution"><a class="source" href="https://www.boston.gov/departments/environment/climate-ready-east-boston">City of Boston</a></span>
</figcaption>
</figure>
<p>By starting with an adaptive design, the U.S. can save billions of dollars compared with having to build new systems decades down the road. The recent renovations of California’s Folsom Dam, built in 1955, illustrate that cost. A <a href="https://www.spk.usace.army.mil/Missions/Civil-Works/Folsom-Dam-Auxiliary-Spillway/">new spillway</a> completed in 2018 cost $900 million – with inflation, that’s about the original cost of the entire dam. </p>
<h2>Adapting for Mississippi River flooding</h2>
<p>When Dutch engineers plan new levees, storm surge barriers and river locks, <a href="https://repository.tudelft.nl/islandora/object/uuid:e893921a-8669-4db1-baec-b64c516bc2ce">they consider</a> what are known as <a href="https://www.stowa.nl/deltafacts/waterveiligheid/innovatieve-dijkconcepten/deltascenarios-en-adaptief-deltamanagement">the Delta Scenarios</a> – four possible futures for flood risk and sea level rise, ranging from moderate to extreme global warming. These scenarios create a framework for adaptive design.</p>
<figure class="align-right ">
<img alt="Photo looking through a lock along the river." src="https://images.theconversation.com/files/392335/original/file-20210329-21-2pz15f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/392335/original/file-20210329-21-2pz15f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=899&fit=crop&dpr=1 600w, https://images.theconversation.com/files/392335/original/file-20210329-21-2pz15f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=899&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/392335/original/file-20210329-21-2pz15f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=899&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/392335/original/file-20210329-21-2pz15f.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1129&fit=crop&dpr=1 754w, https://images.theconversation.com/files/392335/original/file-20210329-21-2pz15f.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1129&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/392335/original/file-20210329-21-2pz15f.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1129&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An example of a river lock.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/closed-sluice-gate-at-the-ecluse-de-tihange-lock-on-the-news-photo/601041116">Arterra/Universal Images Group via Getty Images</a></span>
</figcaption>
</figure>
<p>For example, a complex of locks on the Meuse River, used to raise and lower ships and barges as they travel up- or downstream, <a href="https://repository.tudelft.nl/islandora/object/uuid:e893921a-8669-4db1-baec-b64c516bc2ce">needs to be replaced or rehabilitated</a>. A new lock complex must have enough sluice gates, which can be closed or opened to allow high water through after storms, so the water doesn’t flood surrounding farms and cities. The accompanying weir – the low dam that raises the river’s level – must be high enough to retain enough water for ship operations during times of drought.</p>
<p>Building a tall weir with many sluice gates, and raising riverbank levees to match, would allow the lock complex to manage future climate scenarios, but that would be expensive. With adaptive design, the complex can instead be built to be easily modified later to meet changing climate needs. That includes reserving space for additional sluice gates, and designing gates that can be made taller by welding on additional components as needed.</p>
<p>[<em>Get facts about coronavirus and the latest research.</em> <a href="https://theconversation.com/us/newsletters/the-daily-3?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=coronavirus-facts">Sign up for The Conversation’s newsletter.</a>]</p>
<p>On the Mississippi River and its tributaries, many of the old lock complexes that raise and lower the barges carrying agricultural products and industrial materials are now <a href="https://www.lrl.usace.army.mil/Missions/Civil-Works/Navigation/Locks-and-Dams/Olmsted-Locks-and-Dam/">undergoing replacement</a>. Using similar adaptive design techniques would be a cost-efficient way to face an uncertain future.</p><img src="https://counter.theconversation.com/content/153869/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jeremy Bricker receives funding from the European Union's Horizon 2020 program, the Dutch Research Council, and the TKI Delta Technology program. </span></em></p>With adaptive design, infrastructure is ready to be expanded in the future. It’s working for the Dutch.Jeremy Bricker, Associate Professor of Civil and Environmental Engineering, University of MichiganLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1413502020-11-12T13:27:03Z2020-11-12T13:27:03ZSmart concrete could pave the way for high-tech, cost-effective roads<figure><img src="https://images.theconversation.com/files/351109/original/file-20200804-18-x6ho64.jpg?ixlib=rb-1.1.0&rect=15%2C0%2C5160%2C3445&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The Golden Gate Bridge in San Francisco averages more than 100,000 vehicles daily.</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/tw1CjEGyUUI">Photo by Saketh Garuda for Unsplash</a></span></figcaption></figure><p>Every day, Americans travel on roads, bridges and highways without considering the safety or reliability of these structures. Yet much of the transportation infrastructure in the U.S. is outdated, deteriorating and badly in need of repair. </p>
<p>Of the <a href="https://www.infrastructurereportcard.org/wp-content/uploads/2017/01/Bridges-Final.pdf">614,387 bridges</a> in the U.S., for example, 39% are older than their designed lifetimes, while nearly 10% are structurally deficient, meaning they could begin to break down faster or, worse, be vulnerable to catastrophic failure. </p>
<p>The cost to repair and improve nationwide transportation infrastructure ranges from nearly <a href="https://www.infrastructureusa.org/the-interstate-highway-system-turns-60-challenges-to-its-ability-to-continue-to-save-lives-time-and-money/">US$190 billion</a> to <a href="https://www.artba.org/government-affairs/policy-statements/highways-policy/">almost $1 trillion</a>. Repairing U.S. infrastructure costs individual households, on average, about <a href="https://www.infrastructurereportcard.org/wp-content/uploads/2016/05/ASCE-Failure-to-Act-Report-for-Web-5.23.16.pdf">$3,400 every year</a>. Traffic congestion alone is estimated to cost the average driver <a href="https://inrix.com/press-releases/2019-traffic-scorecard-us/">$1,400</a> in fuel and <a href="https://static.tti.tamu.edu/tti.tamu.edu/documents/mobility-report-2019.pdf">time spent commuting</a>, a nationwide tally of <a href="https://www.infrastructurereportcard.org/wp-content/uploads/2019/02/Full-2017-Report-Card-FINAL.pdf">more than $160 billion per year</a>. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/6HpaCVGeSHc?wmode=transparent&start=1" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Purdue engineering lab has installed smart technology in three Indiana interstate highways.</span></figcaption>
</figure>
<p>I am a <a href="https://scholar.google.com/citations?user=iAdjF78AAAAJ&hl=en">professor</a> in the Lyles School of Civil Engineering and the director of the <a href="https://engineering.purdue.edu/CII/index_html">Center for Intelligent Infrastructures</a> at Purdue University. My co-author, <a href="https://scholar.google.com/citations?user=8k5XKIwAAAAJ&hl=en">Vishal Saravade</a>, is part of my team at the <a href="https://engineering.purdue.edu/SMARTLab">Sustainable Materials and Renewable Technology (SMART) Lab</a>. The SMART Lab researches and develops new technologies to make American infrastructure “intelligent,” safer and more cost-effective. These new systems self-monitor the condition of roads and bridges quickly and accurately and can, sometimes, even repair themselves. </p>
<h2>Smart, self-healing concrete</h2>
<p>Infrastructure – bridges, highways, pavement – deteriorates over time with continuous use. The life of structures could be extended, however, if damages were monitored in real time and <a href="https://www.purdue.edu/newsroom/releases/2020/Q3/expert-tech-that-could-reduce-summer-road-construction.html">fixed early on</a>. In the northern U.S., for example, freeze-thaw cycles in winter cause water to seep into the pavement where it freezes, expands and enlarges cracks, which can cause significant damage. If left unrepaired, this damage may propagate and break down pavements and bridges. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/355016/original/file-20200827-16-16y6zin.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Self-healing concrete embedded with super polymers." src="https://images.theconversation.com/files/355016/original/file-20200827-16-16y6zin.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/355016/original/file-20200827-16-16y6zin.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=223&fit=crop&dpr=1 600w, https://images.theconversation.com/files/355016/original/file-20200827-16-16y6zin.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=223&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/355016/original/file-20200827-16-16y6zin.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=223&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/355016/original/file-20200827-16-16y6zin.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=281&fit=crop&dpr=1 754w, https://images.theconversation.com/files/355016/original/file-20200827-16-16y6zin.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=281&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/355016/original/file-20200827-16-16y6zin.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=281&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Self-healing concrete test study with cracked concrete (left) and self-healed concrete after 28 days (right).</span>
<span class="attribution"><span class="source">SMART Lab/Purdue University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Such damage can be identified and repaired autonomously. At an early stage of a crack, for example, <a href="https://www.purdue.edu/newsroom/releases/2020/Q2/enabling-highways-and-bridges-to-prevent-their-own-damage.html">self-healing pavement</a> would activate super absorbent polymers to absorb water and produce concrete-like material that fills in the crack. Cracks as small as a few microns could be <a href="https://aashtojournal.org/2020/06/12/purdue-researchers-seek-to-create-smart-concrete/">healed to prevent significant damage</a> by preventing or delaying the later stages of the freeze-thaw cycle. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/p-g_0wyhV9E?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The astonishing properties of absorbent polymers.</span></figcaption>
</figure>
<h2>Roadway technology</h2>
<p>Many researchers in the world are working on improving construction infrastructure. Technologies recently being explored include <a href="https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.2019.0439">solar and energy-harvesting roads, charging lanes for electric vehicles, smart streetlights</a> and <a href="https://www.scientificamerican.com/article/cement-producers-are-developing-a-plan-to-reduce-co2-emissions/">reducing carbon-related emissions from construction materials</a>.</p>
<p>At the Purdue SMART Lab, our team is also testing novel sensors that monitor transportation infrastructure by embedding them in several Indiana interstate highways. We plan to expand to other state highway systems in the next few years with a goal to better accommodate <a href="https://theconversation.com/traffic-congestion-reconsidered-111921">increased traffic</a> and provide accurate estimates of road conditions during construction and its life. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/355020/original/file-20200827-16-4sfgrv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/355020/original/file-20200827-16-4sfgrv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/355020/original/file-20200827-16-4sfgrv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/355020/original/file-20200827-16-4sfgrv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/355020/original/file-20200827-16-4sfgrv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/355020/original/file-20200827-16-4sfgrv.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/355020/original/file-20200827-16-4sfgrv.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/355020/original/file-20200827-16-4sfgrv.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Sensors installed on Indiana interstate I-74.</span>
<span class="attribution"><span class="source">Erin Easterling/Purdue University</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Sensors embedded in concrete pavement acquire information about the infrastructure’s health condition in real time and communicate the data to computers. Electrical signals are applied through the sensors. Concrete’s vibrations are converted into electrical signals that are read and analyzed by lab-built customized software. This enables transportation engineers to make effective and data-driven decisions from opening roads to traffic and to proactively identifying issues that cause damage or deterioration. </p>
<p>After concrete is poured for highway pavement, for example, it takes hours to cure and become strong enough to open for traffic. The timing of when to open a highway depends on when the concrete mix is cured. If a roadway opens too early and the concrete is undercured, it can reduce the life expectancy of the pavement and increase maintenance costs. Waiting too long to open a road can result in traffic delays, congestion and increased safety risks for construction workers and commuters. Curing concrete for massive highway projects requires close attention by engineers in conjunction with the weather specific to that region. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/LS0zXtIa2PA?wmode=transparent&start=7" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Sensors embedded in concrete can signal the health of roadways. Video by Erin Easterling/Purdue University.</span></figcaption>
</figure>
<p><a href="https://doi.org/10.1016/j.conbuildmat.2019.07.164">Smart sensors embedded in concrete</a> enable engineers to monitor the infrastructure and make data-driven decisions about when a road can open while retaining maximum life expectancy. Sensors can also help monitor the quality of concrete and whether it is robust enough to withstand traffic flow and corrosion after a roadway is opened. <a href="https://www.evaluationengineering.com/applications/environmental-test/article/21138925/purdue-university-aidriven-monitoringmaintenance-solution-enables-selfhealing-roads-and-bridges">Smart, efficient infrastructure</a> can significantly reduce structural failures, both catastrophic and through normal wear, as well as lead to reduced costs and provide new ways for structural engineers to assess real-time information about the pavement. </p>
<p>[<em>Get our best science, health and technology stories.</em> <a href="https://theconversation.com/us/newsletters/science-editors-picks-71/?utm_source=TCUS&utm_medium=inline-link&utm_campaign=newsletter-text&utm_content=science-best">Sign up for The Conversation’s science newsletter</a>.]</p>
<h2>Saving time and money</h2>
<p>Congress recognizes the need to invest in American transportation systems. A $494 billion legislation package, the <a href="https://transportation.house.gov/imo/media/doc/2020%20INVEST%20in%20America%20Bill%20Summary.pdf">INVEST In America Act</a>, was recently introduced to address America’s deteriorating highways and bridges while diminishing carbon pollution.</p>
<p>Smart sensors and intelligent infrastructure system can enable significant savings of time and money with improved construction safety. Sensors can provide engineers with real-time data of the quality of our infrastructure to make the best decisions for building and maintaining roads, bridges and pavements while improving safety for drivers and construction workers. The addition of self-repairing properties can help build sustainable and long-lasting infrastructure to reduce maintenance and costs.</p><img src="https://counter.theconversation.com/content/141350/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Luna Lu receives funding from Indiana Department of Transportation. </span></em></p><p class="fine-print"><em><span>Vishal Saravade receives funding from Indiana Department of Transportation. </span></em></p>What if roads and bridges could signal structural problems that need repair?Luna Lu, ACPA Scholar & Professor Of Civil Engineering, Purdue UniversityVishal Saravade, Post-doctoral Scientist, Purdue UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1331372020-03-11T14:00:31Z2020-03-11T14:00:31ZJapan’s experience with earthquakes can help teach us to learn to live with floods<p>The intense rainfall from storms this winter <a href="https://www.bbc.co.uk/news/science-environment-51713172">has caused severe flooding</a> in numerous cities across the UK. The storms have left at least eight people dead, and economic losses have been estimated at a few billion pounds. The government has responded by announcing <a href="https://www.bbc.co.uk/news/uk-51784660">flood defence spending will be doubled</a> to £5.2 billion pounds over the next five years. Such severe flooding may seem like a rare event, but – as those living in the most flood-prone areas will tell you – it is not. </p>
<p>There was flooding to a similar if not greater extent between December 2013 and January 2014, which killed 17 people and cost £1.3 billion in economic losses. At the time the Met Office reported that it was the <a href="https://www.channel4.com/news/uk-floods-storms-britain-wettest-winter-on-record">wettest Dececember-January period on record</a>. There was also major flooding across the UK in 2016, and previously in 2009, 2007 and 2000, and flooding of lesser extent in other years as well. </p>
<p>What this suggests is that regularity of major flooding in the UK has dropped from every 15 to 30 years as it was over the 20th century, to between every two to seven years today.</p>
<p>More frequent major flooding puts unprecedented pressure on flood defences, with insufficient time and resources to recover between major events as in the past. We need to acknowledge that in the UK – as is the case elsewhere – flood defences are 20th century approaches now ill-suited to tackle what the 21st century is throwing at us.</p>
<p>Civil engineers have usually been employed to build “hard” structural solutions, such as more and higher concrete walls and soil embankments around rivers. But this may no longer be the best approach in the face of the recurring intense weather patterns and associated flooding. The fundamental assumptions that underpin structural solutions are that the environmental pressures they are built to meet do not substantially change over time. Clearly, this is no longer the case. </p>
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Read more:
<a href="https://theconversation.com/housebuilding-ban-on-floodplains-isnt-enough-flood-prone-communities-should-take-back-control-132468">Housebuilding ban on floodplains isn't enough – flood-prone communities should take back control</a>
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<p>The UK government’s announcement of greater investment in flood defences is welcome, but this does not necessarily mean building longer and higher walls. What is needed is an integrated approach to flood defence that goes beyond using only structural solutions. Now, in the first decades of the century, the UK is in a period of transition that presents the opportunity to adjust our flood defences to the requirements of what this century’s climate will bring. </p>
<h2>How Japan faced up to earthquakes</h2>
<p>In the years before the second world war, Japan faced the issue of building its resilience to earthquakes. Japan experiences on average at least one or two earthquakes of magnitude 6.5 to 7 or greater every year. These earthquakes used to kill many thousands of people, but the average death toll has significantly decreased and has fallen to a few tens of people in recent years (with exceptions, such as the 1995 Kobe earthquake, and the earthquake that caused the 2011 tsunami).</p>
<p>This has been achieved through a programme that combines technological development and significant public involvement. Japan holds annual and even monthly <a href="https://www.bbc.co.uk/newsround/35463098">earthquake drills in schools</a> and other <a href="https://www.japantimes.co.jp/news/2013/09/01/national/annual-quake-drills-take-nankai-twist/#.XmaUfKj7SUk">public and private sector organisations</a>. There is also earthquake education in schools and public information campaigns as well as nationwide earthquake warning messages <a href="https://www.technologyreview.com/s/423288/cellular-technology-that-told-japan-an-earthquake-was-coming/">through mobile phones</a>. In earthquake or tsunami danger zones there are detailed signs to <a href="https://www.japantimes.co.jp/news/2013/10/21/reference/elevation-signs/">indicate areas at risk</a>. </p>
<p>These social approaches are pillars of Japan’s earthquake resilience programme, standing alongside the cutting-edge technological development of recent decades, such as <a href="https://www.tandfonline.com/doi/abs/10.1080/13632460509350537">seismic base isolation and motion-absorbing technology</a>. </p>
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<p>The main outcome of Japan’s public education campaign has been that most people understand that while earthquakes cannot be prevented, their destructive impacts can be minimised, and that everyone has a role to play. This has been instrumental in bringing government and public together in building a more earthquake-resilient society. In fact, Japan has turned its massive challenge to an opportunity: protecting its economy and communities against earthquakes while becoming the leader in earthquake-mitigation technologies: state-of-the-art know-how that it exports to the world.</p>
<p>Many nations worldwide struggle with flooding. Along with the Netherlands, Britain has been a pioneer in flood defence infrastructure engineering. This is an opportunity for the UK to not only address its flooding problems properly at home, but also to build on its existing reputation and take a leading role worldwide in developing new flood defence technology.</p>
<h2>Facing up to floods at home</h2>
<p>To begin with, an information campaign is needed to inform the public of the new reality. Everyone should know that flooding is now a frequent risk – it may have been affordable to get flooded every 15 to 30 years in the past, but few can bear the expense of being flooded out of their home every few years as is possible now. </p>
<p>The public must be properly informed that it is not technically possible to achieve zero flooding – and that in order to protect larger, denser populations in towns and cities, it may be necessary to accept flooding in other areas. </p>
<p>Politicians and experts need to be honest with communities living in flood-prone areas that, given the current circumstances and the potential for the situation worsening in the future, there will need to be a <a href="https://theconversation.com/giant-sandscaping-plan-to-save-norfolk-coast-will-only-put-off-the-inevitable-121346">managed retreat</a> from areas deemed to too difficult or costly to protect.</p>
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<a href="https://theconversation.com/flooding-britains-coastal-towns-and-villages-face-a-design-challenge-to-cope-with-climate-emergency-117448">Flooding: Britain's coastal towns and villages face a design challenge to cope with climate emergency</a>
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<p>And people need to understand that pouring concrete everywhere is not the answer. Greater walls and hard surface areas serve only to guide rainwater into the river channel, which then subsequently bursts its banks. Instead, it would be better to strive to keep surfaces in their natural, permeable states through more widespread use of <a href="https://www.bgs.ac.uk/research/engineeringGeology/urbanGeoscience/SUDS/what.html">sustainable drainage systems</a>. </p>
<p>The storms that sweep across Europe form thousands of miles away in the Atlantic Ocean or in the deserts of North Africa – highlighting the importance of international cooperation to identify and coordinate actions to minimise the effects of global warming. At home, regular flood drills and flood education combined with flood signage in communities at risk are avenues that need to be pursued seriously. </p>
<p>In the medium and long term, these efforts may help everyone understand that flooding is not a rare occurrence nor a one-off problem to be solved, but a natural phenomenon to be lived with. Flooding cannot be prevented, but the way we approach it can bring relief, and opportunities, for our communities and economy.</p><img src="https://counter.theconversation.com/content/133137/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mohammad Heidarzadeh does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Japan took a fresh approach to ensuring their society was more resilient to the frequent earthquakes they experience. We could learn from its experience.Mohammad Heidarzadeh, Assistant Professor in Civil and Environmental Engineering, Brunel University LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1214232019-08-05T12:56:57Z2019-08-05T12:56:57ZWhaley Bridge dam collapse is a wake-up call: concrete infrastructure will not last forever without care<p>Torrential rain in the Midlands and North of England that saw <a href="https://news.sky.com/story/uk-weather-flooding-and-travel-chaos-as-half-a-months-rain-falls-in-one-day-11772254">half a month’s rain fall in one day</a> caused such volumes of water to pass through the spillway of the Toddbrook Reservoir dam, above the town of Whaley Bridge in Derbyshire, that the protective concrete facing was damaged – badly enough to put the dam at risk of a full collapse. </p>
<p>Were the dam to fail this would be the <a href="https://www.engineersireland.ie/EngineersIreland/media/SiteMedia/groups/Divisions/civil/Historic-Dam-Failures-slides.pdf?ext=.pdf">first dam breech in the UK</a> since 1925, when the <a href="https://www.dailypost.co.uk/news/north-wales-news/easter-monday-walk-conwy-snowdonia-14001556">Llyn Eigiau dam burst when its foundations failed</a> in Wales, and its floodwaters overtopped the Coedty reservoir dam downstream, causing it to also fail and flood the valley at the cost of 16 lives. With emergency work underway and more rain forecast, this is still a very real possibility for the Whaley Bridge dam.</p>
<p>The dam above Whaley Bridge is an <a href="https://www.britannica.com/technology/earthfill-dam">earthfill or embankment dam</a> built in the 1830s using a mix of soil and gravel. The massive volume of water cascading down through the hills of Derbyshire’s Peak District from the heavy rain meant the floodwaters increased the reservoir water level up to the dam’s crest and onto the concrete spillway. Most dams are equipped with these concrete structures for the safe and controlled release of excessive flood water downstream.</p>
<p>But in Whaley Bridge the concrete spillway has collapsed under the torrent of high-speed waters, leaving a substantial hole across about a fifth of the face of the spillway. In fact, the current concrete spillway was installed at Whaley Bridge in around 1969 after it suffered similar damage in the winter of 1964. </p>
<p>Spillways are vital for the safety of earthfill dams: they are a hardy protective layer over the earth embankment itself, without which a sustained overtopping of water can wash away the entire dam very quickly. Overtopping of earthfill dams is strictly prohibited: waters should instead be channelled only through the concrete spillway. Earthfill dam failures from overtopping due to heavy rainfall have happened before, for example the Niedow earthfill dam break in Poland in 2010, where the dam was <a href="https://core.ac.uk/download/pdf/82615152.pdf">fully washed away in less than an hour</a>. The spillway of the Oroville Dam in California also <a href="https://www.bbc.co.uk/news/world-us-canada-38952847">collapsed under a torrent of floodwater</a> and required major repairs, although the dam survived intact.</p>
<p>When the spillway is damaged as at Whaley Bridge, the dam is essentially defenceless against further flooding. As rainfall continues, these holes can become larger, further eroding the dam body and weakening its strength against the force of the reservoir water behind it.</p>
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<h2>Battling the forces of nature</h2>
<p>It should be clear then that earthfill dams are extremely vulnerable without the protection of their spillways. At almost 50 years old, the thin grey line of concrete protecting the town of Whaley Bridge from the reservoir just a mile away has reached the end of its life. To fail to invest in and maintain these structures is reckless. </p>
<p>In the case of Toddbrook Reservoir, images of the damaged spillway may point to lack of enough maintenance. Drone footage <a href="https://www.youtube.com/watch?v=_pOu5AHJ1U8">shot by Miles Haslam in 2016</a> shows plants and grass growing on the surface of the spillway. This could mean the concrete surface may have already been cracked, or even that the foundation of the concrete spillway had been undermined, allowing plant life to grow. All this should be subject to a future investigation. </p>
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<p>Concrete surfaces must be maintained and kept smooth and clean, without any cracks or holes. With water pouring across the spillway at very high speeds of up to 60-70mph, any small crack or hole will be subject to tremendous forces that will accelerate erosion damage. This is similar to the damaging effect of hitting a pothole in the road when driving at high speeds. </p>
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<a href="https://theconversation.com/oroville-dam-danger-shows-how-trump-could-win-big-on-infrastructure-73217">Oroville dam danger shows how Trump could win big on infrastructure</a>
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<p>Earthfill dams are the most common type of dams, in Britain and also worldwide, due to the easy availability of soil and gravel materials and their cheaper construction costs. Around 80% of dams worldwide are of the earthfill type. According to the <a href="https://britishdams.org/about-dams/dam-information/types-of-dam/">British Dam Society</a> there are around 3,000 dams of varying sizes in the UK. </p>
<p>Given the Whaley Bridge dam incident, it’s essential that these dams are rigorously inspected to monitor the structural condition of their spillways and their water discharge capacity. The normal lifetime of concrete structures such as these is around 50 years, beyond which they should be either be extensively rehabilitated, or decommissioned. The intense flooding seen in recent years in the UK and worldwide may suggest that the maximum flood discharge capacity for which these dam spillways were designed has been exceeded, and they must be upgraded, or new spillways added.</p>
<p>It is absolutely clear from <a href="https://www.engineersireland.ie/EngineersIreland/media/SiteMedia/groups/Divisions/civil/Historic-Dam-Failures-slides.pdf?ext=.pdf">data of dam failures in the UK and worldwide</a> that the most common cause is overtopping of the dam due to the spillway’s inadequate capacity to discharge floodwaters, due to damage or design. The lesson from Whaley Bridge dam is that the maintenance of dam spillways cannot be ignored – in any circumstances or at any cost.</p><img src="https://counter.theconversation.com/content/121423/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Mohammad Heidarzadeh receives funding from the Royal Society for a project on the resilience of Indonesia to earthquake and tsunami hazards. </span></em></p>The damage to the dam holding back a reservoir just a mile from the nearest town downriver should focus minds on ensuring civil infrastructure is maintained.Mohammad Heidarzadeh, Assistant Professor in Civil and Environmental Engineering, Brunel University LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1041922018-10-22T10:40:32Z2018-10-22T10:40:32ZThe risk of ‘cascading’ natural disasters is on the rise<figure><img src="https://images.theconversation.com/files/241521/original/file-20181021-105776-nsc3mq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Deadly debris flows came to Los Angeles after heavy rain pounded wildfire-scarred land.</span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/California-Storms/8ab3c45da86649188f5e56d45e3e81bc/3/0">AP Photo/Reed Saxon</a></span></figcaption></figure><p>In a warming world, the dangers from natural disasters are changing. In a <a href="https://www.nature.com/articles/d41586-018-06783-6">recent commentary</a>, we identified a number of costly and deadly catastrophes that point to an increase in the risk of “cascading” events – ones that intensify the impacts of natural hazards and turn them into disasters.</p>
<p>Multiple hazardous events are considered cascading when they act as a series of toppling dominoes, such as <a href="https://theconversation.com/post-fire-mudslide-problems-arent-new-and-likely-to-get-worse-90048">flooding and landslides that occur after rain over wildfires</a>. Cascading events may begin in small areas but can intensify and spread to <a href="https://esajournals.onlinelibrary.wiley.com/doi/full/10.1890/1540-9295(2007)5%5B221:CEILEA%5D2.0.CO%3B2">influence larger areas</a>.</p>
<p>This rising risk means decision-makers, urban planners and risk analysts, civil engineers like us and other stakeholders need to invest more time and effort in tracking connections between natural hazards, including hurricanes, wildfires, extreme rainfall, snowmelt, debris flow, and drought, under a changing climate.</p>
<h2>Cascading disasters</h2>
<p><a href="https://www.climate.gov/news-features/blogs/beyond-data/2017-us-billion-dollar-weather-and-climate-disasters-historic-year">Since 1980 to January 2018</a>, natural disasters caused an inflation-adjusted US$1,537.4 billion in damages in the United States. </p>
<p>The loss of life in that period – nearly <a href="https://www.climate.gov/news-features/blogs/beyond-data/2017-us-billion-dollar-weather-and-climate-disasters-historic-year">10,000 deaths</a> – has been mounting as well. The United States has seen more billion-dollar natural disaster events recently than ever before, with climate models projecting an <a href="https://www.sciencedirect.com/science/article/pii/S2212094715300165">increase in intensity and frequency of these events</a> in the future. In 2017 alone, natural disasters resulted in <a href="https://www.climate.gov/news-features/blogs/beyond-data/2017-us-billion-dollar-weather-and-climate-disasters-historic-year">$306 billion losses</a>, setting the costliest disaster year on record. </p>
<p>We decided it was important to better understand cascading and compound disasters because the impacts of climate change can often lead to coupled events instead of isolated ones. The United Nations Office for Disaster Risk Reduction, or UNISDR, <a href="https://www.unisdr.org/we/inform/publications/50226">claims</a>: “Any disaster entails a potentially compounding process, whereby one event precipitates another.”</p>
<p>For example, deforestation and flooding often occur together. When vegetation is removed, top soil washes away and the earth is incapable of absorbing rainfall. The 2004 Haiti flood that killed more than 800 people and left many missing is an example of this type of cascading event. The citizens of the poverty-stricken country destroyed more than <a href="https://www.cbsnews.com/news/haiti-floods-due-to-deforestation/">98 percent</a> of its forests to provide charcoal for cooking. When Tropical Storm Jeanne hit, there was no way for the soil to absorb the rainfall. To further complicate existing issues, trees excrete water vapor into the air, and so a sparser tree cover often yields less rain. As a result, the water table may drop, making farming, which is the backbone of Haiti’s economy, more challenging.</p>
<h2>Rising risk from climate change</h2>
<p>Coupled weather events are becoming more common and severe as the earth warms. Droughts and heatwaves are a coupled result of global warming. As droughts lead to dry soils, the surface warms since the sun’s heat cannot be released as evaporation. In the United States, week-long heatwaves that occur simultaneously with periods of drought are <a href="http://www.pnas.org/content/112/37/11484">twice as likely to happen now as in the 1970s</a>. </p>
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<span class="caption">Higher temperatures raise the chances of drought and wildfires, as they did in Brazil in 2011.</span>
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<p>Also, the severity of these cascading weather events worsens in a warming world. Drought-stricken areas become <a href="http://dx.doi.org/10.1111/gcb.13275">more vulnerable to wildfires</a>. And snow and ice are <a href="http://www.pnas.org/content/early/2018/10/03/1805953115">melting earlier</a>, which is altering the timing of runoff. This has a direct relationship with the fact that the <a href="https://journals.ametsoc.org/doi/full/10.1175/JAMC-D-15-0297.1">fire season across the globe has extended</a> by 20 percent since the 1980s. Earlier snowmelt increases the chance of low flows in the dry season and can make forests and vegetation more vulnerable to fires. </p>
<p>These links spread further as wildfires occur at elevations <a href="https://www.nature.com/articles/d41586-018-06783-6">never imagined before</a>. As fires destroy the forest canopy on high mountain ranges, the way snow accumulates is altered. Snow melts faster since soot deposited on the snow absorbs heat. Similarly, as drought dust is released, snow melts at a higher rate as has been seen in the <a href="https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017GL075826">Upper Colorado River Basin</a>.</p>
<p>Fluctuations in temperature and other climatic patterns can harm or challenge the already crumbling infrastructure in the United States such as dams and levees. The average age of the nation’s dams and levees is over <a href="https://www.infrastructurereportcard.org/">50 years</a>. The deisgn of these aging systems did not account for the effects of cascading events and changes in the patterns of extreme events due to <a href="http://science.sciencemag.org/content/355/6330/1139.2">climate change</a>. What might normally be a minor event can become a major cause for concern such as when an unexpected amount of melt water triggers debris flows over burned land.</p>
<p>There are several other examples of cascading disasters. In July, a deadly <a href="https://www.cbsnews.com/news/death-toll-rises-deadly-greece-wildfires-today-2018-07-29/">wildfire raged through Athens</a> killing 99 people. During the same month on the other side of the world in Mendocino, California, more than 1,800 square kilometers were scorched. For scale, this area is larger than the entire city of Los Angeles.</p>
<p>When landscapes are charred during wildfires, they become more vulnerable to landslides and flooding. In January of this year, a debris flow event in Montecito, California <a href="https://www.sciencedaily.com/releases/2018/05/180530113243.htm">killed 21 people</a> and injured more than 160. Just one month before the landslide, the soil on the town’s steep slopes were destabilized in a wildfire. After a storm brought torrential downpours, a <a href="http://www.latimes.com/local/lanow/la-me-montecito-mudslide-main-20180112-story.html">5-meter high wave of mud</a>, tree branches and boulders swept down the slopes and into people’s homes.</p>
<p>Hurricanes also can trigger cascading hazards over large areas. For example, significant damages to trees and loss of vegetation due to a hurricane increase the chance of landslides and flooding, <a href="https://link.springer.com/article/10.1007/s11069-015-2028-8">as reported in Japan in 2004</a>.</p>
<h2>Future steps</h2>
<p>Most research and practical risk studies focus on estimating the likelihood of different individual extreme events such as hurricanes, floods and droughts. It is often difficult to describe the risk of interconnected events especially when the events are not physically dependent. For example, two physically independent events, such as wildfire and next season’s rainfall, are related only by how fire later raises the chances of landslide and flooding.</p>
<p>As civil engineers, we see a need to be able to better understand the overall severity of these cascading disasters and their impacts on communities and the built environment. The need is more pronounced considering the fact that much of the nation’s critical infrastructure is aged and currently operate under rather <a href="https://www.infrastructurereportcard.org/americas-grades/">marginal conditions</a>. </p>
<p>A first step in solving the problem is gaining a better understanding of how severe these cascading events can be and the relationship each occurrence has with one another. We also need reliable methods for risk assessment. And a universal framework for addressing cascading disasters still needs to be developed. </p>
<p>A global system that can predict the interactions between natural and built environments could save millions of lives and billions of dollars. Most importantly, community outreach and public education must be prioritized to raise awareness of the potential risks cascading hazards can cause.</p><img src="https://counter.theconversation.com/content/104192/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Farshid Vahedifard receives funding from the National Science Foundation and the United States Army Corps of Engineers </span></em></p><p class="fine-print"><em><span>Amir AghaKouchak receives funding from National Science Foundation, National Aeronautics and Space Administration, National Oceanic and Atmospheric Administration, and California Energy Commission. </span></em></p>One natural disaster can exacerbate the effects of others – think landslides after wildfires. This means engineers and planners need to rethink how they assess and prepare for risk.Farshid Vahedifard, CEE Advisory Board Endowed Professor and Associate Professor of Civil and Environmental Engineering, Mississippi State UniversityAmir AghaKouchak, Associate Professor of Civil & Environmental Engineering, University of California, IrvineLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1020552018-09-12T13:32:34Z2018-09-12T13:32:34ZPotholes: how engineers are working to fill in the gaps<figure><img src="https://images.theconversation.com/files/233448/original/file-20180824-149463-1hzm435.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Potholes are a <a href="https://www.rac.co.uk/drive/advice/road-safety/report-a-pothole/">perennial problem</a>. They are dangerous to road users, and the damage they cause to vehicles can be hugely expensive. The cost of repairing them is also vast. But still they appear, and reappear, in countless places. So why do these pesky crevices pose such a difficult challenge? And is there any light at the end of this pothole-filled tunnel?</p>
<p>Potholes often begin as imperceptible microscopic cracks in the road surface. Bad weather, poor drainage and heavy traffic can all cause that surface to loosen and wear away. In 2017, more than <a href="https://www.autocar.co.uk/car-news/industry/potholes-how-much-they-cost-uk-and-how-they-are-fixed">2m potholes</a> were repaired on UK roads, at a cost of some £120m.</p>
<p>At the moment, where and when these microscopic cracks will appear is hard to determine. But in the future it is likely that high precision measuring techniques will be able to predict the time and location that potholes will appear. To repair the road before potholes grow, machines will be installed into autonomous vehicles, cleaning out the damaged areas and filling them in again. </p>
<h2>Self-healing roads</h2>
<p>In the meantime, the development of new types of road material, such as “self-healing” asphalt, something we are investigating at the <a href="https://www.nottingham.ac.uk/research/groups/ntec/index.aspx">Nottingham Transportation Engineering Centre</a>, could reduce the necessary frequency of repairs – and hopefully help turn potholes into a distant memory.</p>
<p>Asphalt roads are composed of mineral aggregates that give structural stability, and bitumen, a viscous liquid that binds the other materials together. When cracks appear in the road, bitumen drains into the cracks and fills them. The problem is that bitumen is a very viscous liquid at normal temperatures, and the healing of the cracks can take weeks. With regular traffic, the rate of crack growth may occur at a faster rate than they are filled – allowing potholes to form. </p>
<p>To accelerate the “healing” of the road, we are exploring the addition of tiny capsules containing asphalt rejuvenators such as sunflower oil, or tall oil, a byproduct of paper production. (The inspiration for the capsules came from watching an episode of the Spanish version of the TV series MasterChef, in which a contestant used a technique to form spheres that resemble caviar when submerged in a liquid.)</p>
<p>The idea is that when roads start to crack, the capsules break open and release the oil within, softening the surrounding asphalt. This helps the asphalt stick back together more swiftly, effectively filling in cracks and preventing small defects from deteriorating. With this idea, we expect to delay the first potholes by at least five years, reducing the need for maintenance and all the troubles that come from it, such as slow traffic and travel delays. </p>
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<h2>Warming things up</h2>
<p><a href="http://www.itv.com/news/2017-01-07/repairing-potholes-could-reach-14-billion-in-two-years-councils-warn/">According to the Local Government Association</a>, road repair bills in England and Wales could soon reach £14 billion, dwarfing the £4.4 billion highways budget of councils. Another solution being investigated at Brunel University – which could save a fortune – is the use of infrared heat to make repairs cheaper and longer-lasting. </p>
<p>Wet weather, combined with cycles of freezing and thawing, dramatically accelerates pothole development – and many repairs fail prematurely. This is because the traditional way to repair potholes with heat is to inject them with boiling hot asphalt. But if the road is cold, the temperature of the repair material falls significantly, creating weaker bonds with the surrounding material. Some new “repaired” patches can start to show deterioration within a few months. </p>
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<p>To increase the performance of asphalt patch repair, the <a href="https://www.brunel.ac.uk/civil-engineering/research-and-phd-programmes/Pavement-Ground-Engineering-Research-Group-PAGE">Pavement and Ground Engineering Research Group</a> at Brunel has developed the <a href="https://www.brunel.ac.uk/news-and-events/news/articles/Infrared-could-absorb-shocking-pothole-repair-bills">Controlled Pothole Repair System</a> (CPRS). This new method uses a portable infrared heating machine to preheat the road surface (and the area below) before making the repair. </p>
<p>The CPRS allows much more precise temperature control, providing much greater bonding strength for the replacement materials. The machine is also designed to be easily transported to repair sites, and is compact enough to be operated within a single lane of the road, so that extensive road closures are avoided.</p>
<p>The aim is to deliver repairs that last a lot longer than their current life expectancy. This will create better quality road surfaces that would make for fewer accidents and smaller maintenance budgets. </p>
<p>We hope that with further research, CPRS can improve asphalt patch repair to last for as long as five years – as opposed to the average of two years that most authorities currently expect with conventional methods. We estimate this could cut costs by 25% to 50%. Rolled out nationwide, it would mean a network of better quality roads, lower maintenance and compensation costs – and fewer accidents.</p><img src="https://counter.theconversation.com/content/102055/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Alvaro Garcia receives funding from EPSRC, European Union, and various industrial partners, including Highways England. He works for the University of Nottingham. </span></em></p><p class="fine-print"><em><span>Juliana Byzyka receives funding from EPSRC. </span></em></p><p class="fine-print"><em><span>Mujib Rahman does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Bumps in the road are dangerous, expensive and difficult to fix.Alvaro Garcia, Lecturer in Engineering, University of NottinghamJuliana Byzyka, PhD Candidate, Brunel University LondonMujib Rahman, Senior Lecturer in Civil Engineering, Brunel University LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1016272018-08-15T17:02:18Z2018-08-15T17:02:18ZGenoa bridge collapse: maintaining these structures is a constant battle against traffic and decay<p>As rescue workers look for survivors in the concrete rubble that used to be part of the Morandi bridge in Genoa, Italian authorities are starting their investigation into the possible causes behind this <a href="https://www.theguardian.com/world/2018/aug/15/genoa-bridge-collapse-death-toll-italy-minister-calls-resignations">terrible tragedy</a>.</p>
<p>It is too early to determine what may have caused the catastrophic collapse of more than 100 metres of the multi-span, cable-stayed suspension bridge, completed just over 50 years ago. But it’s important to understand that bridge engineering does not end when construction finishes and traffic starts to flow. In fact, properly looking after a bridge during its long life is as crucial as having a good design, using high-quality materials, and ensuring sound workmanship during construction.</p>
<p>Modern bridges are designed for a life of 100 years, though many centenarian bridges – such as the Forth Bridge in Scotland, which opened in 1890 – still provide sterling service, and of course there are smaller bridges built of stone to more ancient designs that have stood for many hundreds of years. Considering the number of bridges built in Europe during the expansion of the motorway networks from the late-1950s onwards, we should expect, and be prepared for, many to exceed their planned lifespan in coming decades. Facilitating this is ambitious but necessary, and made possible thanks only to regular inspection and maintenance that ensures that building materials have not degraded, and that structural elements are fit to bear the traffic and environmental loads they face. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/232103/original/file-20180815-2906-1rgrnjy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/232103/original/file-20180815-2906-1rgrnjy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/232103/original/file-20180815-2906-1rgrnjy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=263&fit=crop&dpr=1 600w, https://images.theconversation.com/files/232103/original/file-20180815-2906-1rgrnjy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=263&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/232103/original/file-20180815-2906-1rgrnjy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=263&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/232103/original/file-20180815-2906-1rgrnjy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=330&fit=crop&dpr=1 754w, https://images.theconversation.com/files/232103/original/file-20180815-2906-1rgrnjy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=330&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/232103/original/file-20180815-2906-1rgrnjy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=330&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
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<span class="caption">The Forth Bridge outside Edinburgh, one of Britain’s iconic bridges, is more than 100 years old.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Scotland-2016-Aerial-Edinburgh-Forth_Bridge.jpg">Andrew Shiva</a></span>
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<p>So what are the factors that affect the strength of a bridge and may compromise public safety?</p>
<h2>Environment and climate</h2>
<p>The climate in a bridge’s location, taken alongside atmospheric pollution common in cities, can have an adverse influence on the material of the bridge – for example, the corrosion of steel reinforcement or pre-stressed steel tendons embedded in concrete. Regular inspections are typically scheduled every six years for large bridges to identify any degradation, and to take appropriate measures to replace cracking concrete and corroded steel, or to introduce protective coatings. </p>
<p>In England, the <a href="http://mat.pixl8-hosting.co.uk/en/motorways/motorway-listing/m6/m5-j1-to-j3-and-m6-j13-to-j1-midland-links-motorways/index.cfm">Midlands Link motorway viaducts</a>, comprising 13 miles of elevated motorway carrying the M5 and M6 motorways around Birmingham, suffered from chloride-induced steel corrosion early on in their life from exposure to salt used to de-ice the roads. This required an extensive application of corrosion protection measures in the early 1990s. More than 700 structures have benefited from this action, <a href="https://icevirtuallibrary.com/doi/10.1680/bren.12.00015">demonstrating</a> the cost savings that can be made if appropriate action is taken at the right time.</p>
<h2>Stress and fatigue</h2>
<p>Fatigue caused by use is another factor, and inspectors will look out for tell-tale signs of failure often associated with the cyclical stress produced by passing vehicles, particularly heavy trucks. This type of failure is especially relevant for <a href="http://epubs.surrey.ac.uk/795965/3/Causes%20and%20Consequences.pdf">metal bridge decks</a> and the cables of suspension and cable-stayed bridges. Traffic has increased ever since these bridges were built, which inevitably leads to the need for more maintenance and strengthening work, such as additional steel, glass or carbon fibre-reinforced plates on critical parts in order to restore or enhance their strength compared to what was deemed necessary during their design. For example, Network Rail in the UK used <a href="https://www.icevirtuallibrary.com/doi/10.1680/eacm.2009.162.3.119">fibre-reinforced polymers</a> to strengthen more than 20 bridges carrying highway or railway traffic between 2001 and 2010.</p>
<p>Consider how we all tend to react to a road sign bearing the words: “Essential Bridge Works – Expect Long Delays”. One such situation prompted this <a href="https://www.staffordshire-live.co.uk/news/burton-news/bridge-closure-looks-cause-havoc-378287">comment from a member of the public</a>: “We are doomed. I am going to buy a tent and pitch it outside work for the three months while the misery goes on.” Perhaps knowing why this is necessary – and the consequences of not doing so – might persuade people to reconsider such views.</p>
<h2>Money and willingness to spend it</h2>
<p>Equally, we must understand that maintenance budgets need to be set at levels that far exceed those that would allow engineers only to “firefight” the most severe problems, <a href="https://www.transport-network.co.uk/Backlog-on-local-British-bridge-repairs-jumps-by-1bn/14756">as is becoming worryingly commonplace</a>. Instead, budgets need to allow for planned interventions and necessary upgrades over many decades. That requires public and government support, as well as skilled engineers committed to ensuring the safety of an ageing structure. </p>
<p>There are challenges in devising improved methods to assess bridge strength, developing new repair techniques, and new ways of collecting and using inspection and monitoring data to provide advance warning of problems. These constantly push technological boundaries, making it possible to operate existing bridges safely during their long service lives. And the experience gained feeds into new designs that will become reality in years to come.</p>
<p>Those investigating the collapse of the Morandi bridge will look at inspection and maintenance matters. Other lines of enquiry will no doubt include the unusual design of the multi-span bridge, with only a few cable stays to transfer deck loads to the towers, the ongoing work to shore up the foundations, and the heavy rainfall at the time of the collapse. In the shadow of this terrible loss of life, it is worth remembering that bridge inspection and maintenance may be annoying for commuters – but it is crucial.</p><img src="https://counter.theconversation.com/content/101627/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Marios Chryssanthopoulos has received funding from EPSRC, Network Rail and the Highways Agency for research on bridge safety.</span></em></p>Bridge engineering does not end when construction finishes and traffic starts to flow.Marios Chryssanthopoulos, Professor of Structural Systems, University of SurreyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1014992018-08-15T11:33:38Z2018-08-15T11:33:38ZIndonesia earthquake: how scrap tyres could stop buildings collapsing<figure><img src="https://images.theconversation.com/files/232066/original/file-20180815-2891-6hbtvz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Collapsed building after 2018 Lombok earthquake.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/indonesia-lombok-august-9-2018-buildings-1154843722?src=er3k8KiQs_MtOYxhU-AM-w-1-0">Shutterstock</a></span></figcaption></figure><p>At the time of writing, <a href="https://www.cnn.com/2018/08/13/asia/lombok-earthquake-intl/index.html">436 people have died</a> following an earthquake in the Indonesian island of Lombok. A further 2,500 people have been hospitalised with serious injuries and over 270,000 people have been displaced.</p>
<p>Earthquakes are one of the deadliest natural disasters, accounting for just 7.5% of such events between 1994 and 2013 but causing <a href="https://www.emdat.be/sites/default/files/adsr_2016.pdf">37% of deaths</a>. And, as with all natural disasters, it isn’t the countries that suffer the most earthquakes that see the biggest losses. Instead, the number of people who die in an earthquake is related to <a href="https://www.cred.be/downloadFile.php?file=sites/default/files/PubID266Earthquakes.pdf">how developed</a> the country is.</p>
<p>In Lombok, as <a href="https://edition.cnn.com/2015/05/10/asia/nepal-earthquake-death-toll/">in Nepal in 2015</a>, many deaths were caused by the widespread collapse of local rickety houses incapable of withstanding the numerous aftershocks. More generally, low quality buildings and inadequate town planning are the <a href="https://www.emdat.be/sites/default/files/adsr_2016.pdf">two main reasons</a> why seismic events are more destructive in developing countries.</p>
<p>In response to this issue, my colleagues and I are working on a way to create cheap building foundations that are better at absorbing seismic energy and so can prevent structures from collapsing during an earthquake. And the key ingredient of these foundations is rubber from scrap tyres, which are otherwise very difficult to safely dispose of and are largely <a href="https://www.thehindu.com/business/Turning-waste-tyre-into-%25E2%2580%2598green-steel%25E2%2580%2599/article14518524.ece">sent to landfill</a> or burnt, releasing large amounts of carbon dioxide and toxic gases containing heavy metals. </p>
<h2>Rubber-soil mixture</h2>
<p>Previous attempts to protect buildings from earthquakes by altering their foundations have shown promising results. For example, a recently developed underground <a href="https://theconversation.com/our-new-anti-earthquake-technology-could-protect-cities-from-destruction-44028">vibrating barrier</a> can reduce between 40% and 80% of surface ground motion. But the vast majority of these sophisticated isolation methods are expensive and very <a href="https://www.researchgate.net/publication/263556747_Seismic_isolation_for_low-to-medium-rise_buildings_using_granulated_rubber-soil_mixtures_Numerical_study">hard to install</a> under existing buildings.</p>
<p>Our alternative is to create foundations made from local soil mixed with some of the <a href="http://www.etrma.org/uploads/Modules/Documentsmanager/elt-report-v9a---final.pdf">15m tonnes</a> of scrap tyre produced annually. This rubber-soil mixture can reduce the effect of seismic vibrations on the buildings on top of them. It could be easily retrofitted to existing buildings at low cost, <a href="https://www.researchgate.net/publication/262894408_Seismic_isolation_using_granulated_tire-soil_mixtures_for_less-developed_regions_Experimental_validation">making it particularly suitable for developing countries</a>. </p>
<p><a href="https://www.researchgate.net/publication/234720015_Dynamic_properties_of_dry_sandrubber_SRM_and_gravelrubber_GRM_mixtures_in_a_wide_range_of_shearing_strain_amplitudes">Several investigations</a> have shown that introducing rubber particles into the soil can increase the amount of <a href="https://www.researchgate.net/publication/326573152_Dynamic_behaviour_of_shredded_rubber_soil_mixtures">energy it dissipates</a>. The earthquake causes the rubber to deform, absorbing the energy of the vibrations in a similar way to how the outside of a car <a href="https://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/crumple-zone.htm">crumples in a crash</a> to protect the people inside it. The stiffness of the sand particles in the soil and the friction between them helps maintain the consistency of the mixture.</p>
<p>My colleagues and I <a href="https://www.researchgate.net/project/The-use-of-rubber-sand-mixtures-RSM-for-the-mitigation-of-earthquake-damage-in-structures?_sg=Lt6JDvLryAwjsLhMrpPu5DZ0IhUMO5LKobDzL6YDAfcF_Rc6ZYA0HGAabGeV10GzT_hRYcIgZkjne9GrWuYGGID_b_hsxIjSiJ5-">have shown</a> that introducing rubber-soil mixture can also change the natural frequency of the soil foundation and how it interacts with the structure above it. This could help avoid a well-known resonance phenomenon that occurs when the seismic force has a similar frequency to that of the natural vibration of the building. If the vibrations match they will accentuate each other, dramatically amplifying the shake of the earthquake and causing the structure to collapse, as happened in the famous case of the <a href="http://www.wsdot.wa.gov/tnbhistory/connections/connections3.htm">Tacoma Narrows bridge in 1940</a>. Introducing a rubber-soil mixture can offset the vibrations so this doesn’t happen. </p>
<h2>A promising future</h2>
<p>The key to making this technology work is finding the optimum percentage of rubber to use. Our preliminary calculations echo <a href="https://www.researchgate.net/publication/229742536_Seismic_isolation_by_rubber-soil_mixtures_for_developing_countries">other investigations</a>, indicating that a layer of rubber-soil mixture between one and five metres thick beneath a building would reduce the maximum horizontal acceleration force of an earthquake by between 50% and 70%. This is the most destructive element of an earthquake for residential buildings. </p>
<p>We are <a href="https://www.napier.ac.uk/research-and-innovation/impact-case-studies/from-cycle-paths-to-seismic-maths">now studying how different shaped rubber-soil mixture</a> foundations could make the system more efficient, and how it is affected by different types of earthquake. Part of the challenge with this research is testing the system. We build <a href="https://youtu.be/bIqV95gIf9o">small-scale table models</a> to try to understand how the system works and assess the accuracy of computer simulations. But testing it in the real world requires an actual earthquake, and it’s almost impossible to know exactly when and where one will strike.</p>
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<p>There are ways of testing it through large scale experiments, which involve creating full-size model buildings and shaking them to simulate the force from recorded real earthquakes. But this needs funding from big institutions or companies. Then it is just a question of trying the solution on a real building by convincing the property owners that it’s worthwhile.</p><img src="https://counter.theconversation.com/content/101499/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Juan Bernal-Sanchez works for Edinburgh Napier University. </span></em></p>Researchers are using a rubber-soil mixture to make earthquake-proof foundations.Juan Bernal-Sánchez, PhD Resarcher, Edinburgh Napier UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/979002018-06-13T12:39:37Z2018-06-13T12:39:37ZPredicting the World Cup winner: An engineer’s working guide<figure><img src="https://images.theconversation.com/files/222799/original/file-20180612-112602-iiml7j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">One of the favourites to win the World Cup, Germany's national football team, on their way to Russia.</span> <span class="attribution"><span class="source">Armando Babani/EPA</span></span></figcaption></figure><p>As a civil engineer I’m fascinated by predictions of who will win the FIFA World Cup finals in Russia, seeing that we use predictions on a regular basis in engineering. For the finals, there’s a wide variety of forecasts. In addition to armchair fans’ predictions, there are those by the seasoned <a href="https://www.theguardian.com/football/series/world-cup-2018-guardian-experts-network">football experts</a>. Then there are the <a href="https://www.standard.co.uk/sport/football/worldcup/germany-vs-mexico-world-cup-2018-prediction-tv-live-stream-online-betting-tips-odds-time-lineups-a3859526.html">predictions</a> based on betting tips.</p>
<p>In a completely different class are the quirky animal “predictions” that belong between inverted commas. The most famous was celebrated <a href="https://www.bbc.com/news/world-europe-11626050">Paul the Octopus</a> who correctly predicted the outcome of eight matches in the 2010 World Cup finals. This year, the oracle’s job has gone to <a href="http://www.thehindu.com/sport/football/meet-achilles-the-cat-russias-successor-to-paul-the-octopus/article24121718.ece">Achilles</a>, a deaf white cat from St Petersburg’s Hermitage museum in Russia. With 50 other cats, Achilles’s day job is to keep the museum free of rodents.</p>
<p>A vet who oversees Achilles explained why he was picked for the new soothsayer job:</p>
<blockquote>
<p>We went for Achilles because he is beautiful, first of all, but also because — like all white cats with blue eyes — he is deaf, so he has a great deal of intuition, he sees with his heart.</p>
</blockquote>
<h2>Stable relationships</h2>
<p>But it won’t only be Achilles who’ll be using intuition. When humans predict which team will lift the FIFA World Cup Trophy on 15 July at the Luzhniki Stadium in Moscow, intuition will guide most of them. Will it be Germany or Brazil, perhaps Tunisia or Egypt? Intuitively Brazil or Germany seem better bets than Tunisia or Egypt.</p>
<p>Often our intuitions can be wrong as they are based on heuristics (rules of thumb) or biases (prejudices). Consider Egypt or Tunisia’s upcoming performance. Perhaps Egypt will do better: their superstar striker Mohamed Salah, who plays for Liverpool in the English Premier League, won <a href="http://www.dailymail.co.uk/sport/football/article-5721045/The-34-individual-awards-Mohamed-Salah-won-Liverpool-season.html">34 individual awards</a> this season. They include the Premier League Golden Boot winner after scoring a record 32 goals in 36 league games. With him there, Egypt must therefore be a good team.</p>
<p>Less well known perhaps is that Tunisia are currently <a href="http://www.fifa.com/fifa-world-ranking/ranking-table/men/index.html">ranked</a> 21st and Egypt 46th. Going for Egypt is an example of decisions that are based on what information readily comes to mind.</p>
<p>Professionals in my field of civil engineering make decisions about how structures behave when loaded. For example how an office block’s foundations will behave when loaded by users. This often requires using intuition to interpret data. Intuition is sometimes seen as unscientific but <a href="https://theconversation.com/is-it-rational-to-trust-your-gut-feelings-a-neuroscientist-explains-95086">recent research</a> has shown that it is often vital to making decisions.</p>
<p>Nobel laureate <a href="https://www.mckinsey.com/business-functions/strategy-and-corporate-finance/our-insights/strategic-decisions-when-can-you-trust-your-gut">Daniel Kahneman and psychologist Gary Klein</a> <a href="http://dx.doi.org/10.1037/a0016755">suggest</a> that intuitive expertise can only develop in environments in which there are stable relationships between identifiable cues and events. </p>
<p>Cues in football could be relative team rankings and events could be wins or losses. Cues in civil engineering could be material strengths and outcomes could be structures that do not fail. Individuals still require time to learn patterns in “high validity” environments, such as civil engineering, but judgements in such environments can often be trusted.</p>
<p>Do football outcomes show stable relationships? To find out, I collected official team rankings before the last five FIFA World Cups, along with game outcomes. Outcomes between similar ranked teams (ranking difference less than 11) are compared to outcomes between disparate teams (ranking difference greater than 11) in the figure below.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/222778/original/file-20180612-112605-kqhmdy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222778/original/file-20180612-112605-kqhmdy.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222778/original/file-20180612-112605-kqhmdy.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222778/original/file-20180612-112605-kqhmdy.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222778/original/file-20180612-112605-kqhmdy.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222778/original/file-20180612-112605-kqhmdy.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222778/original/file-20180612-112605-kqhmdy.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Outcomes at last 5 FIFA World Cups (Data: fifa.com, Analysis: Charles MacRobert)</span>
</figcaption>
</figure>
<p>The stronger (higher ranked) of similar ranked teams won 50%, drew 28% and lost 22% of games; for disparate teams the stronger team won 58%, drew 21% and lost 21% of games. Outcomes become marginally more predictable as the disparity between teams increases. However, it seems very difficult to accurately predict outcomes based on which teams were playing better before respective FIFA World Cups.</p>
<p>An argument can be made that using rankings does not take into account enough cues. In 2014 Goldman Sachs using a <a href="https://theconversation.com/world-cup-2014-predictions-who-will-take-the-title-27387">much larger pool</a> of cues only managed to correctly predict 58% of knockout stage teams. Using the FIFA rankings before the 2014 FIFA World Cup would have predicted 64% of outcomes (the most predictable of the last five). Therefore using rankings seems an adequate metric.</p>
<p>How does this compare to predictions in civil engineering? Accepted norms are that building foundations are designed so that the annual probability of failure does not exceed 1%, but for large dams this figure is 0.01%. As the consequence of a large dam failing is much greater, the probability of this occurring must be lower. So engineers need to correctly predict 99% of building foundation outcomes and 99.99% of large dam outcomes.</p>
<p>Getting such low probabilities of failure takes considerable analysis. An important aspect of large dams constructed from earth is the stability of the earth embankment. A recent study showed that very experienced engineers could <a href="http://journals.co.za/content/journal/10520/EJC-7836f61c3">correctly predict</a> the stability of a soil slope in 80% of cases without any calculations. </p>
<p>Less experienced engineers were only successful in 66% of cases and untrained students were successful in 49%. Students could increase their success rate to 64% after a <a href="https://ascelibrary.org/doi/10.1061/%28ASCE%29EI.1943-5541.0000382">training exercise</a>. </p>
<p>But although fairly good predictions could be made purely on gut instinct, prudent engineers should not base designs purely on intuition. Even in engineering where there is sufficient regularity in the behaviour of structures, it is difficult to fully internalise the patterns presented between cues and outcomes. The ability to internalise patterns in sports outcomes is likely to be even harder.</p>
<h2>Trust expert predictions?</h2>
<p>So can we trust expert predictions of football outcomes? Perhaps, but football is very variable and placing too much faith in expert predictions may be unwise. With this disclaimer in place, a civil engineer’s prediction of outcomes will be made for the upcoming 2018 FIFA World Cup.</p>
<p>Using 20 000 simulations of the upcoming FIFA World Cup, based on the current FIFA rankings, the top 16 teams that could win are shown below along with the percentage of simulations won by each. Germany seem a better bet than Tunisia but remember the statistics show a large amount of variability. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/222591/original/file-20180611-191978-rh5aq2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/222591/original/file-20180611-191978-rh5aq2.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=360&fit=crop&dpr=1 600w, https://images.theconversation.com/files/222591/original/file-20180611-191978-rh5aq2.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=360&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/222591/original/file-20180611-191978-rh5aq2.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=360&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/222591/original/file-20180611-191978-rh5aq2.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=452&fit=crop&dpr=1 754w, https://images.theconversation.com/files/222591/original/file-20180611-191978-rh5aq2.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=452&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/222591/original/file-20180611-191978-rh5aq2.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=452&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Potential world cup winners (Data: fifa.com, Analysis: Charles MacRobert)</span>
</figcaption>
</figure>
<p>So pick a team you think will win, hope they sing their <a href="https://theconversation.com/why-football-teams-who-sing-their-national-anthem-with-passion-are-more-likely-to-win-96765">national anthem with passion</a>, enjoy following their games and don’t be too disappointed when they lose. An analytical assessment of the results suggests this is the most intuitive approach.</p><img src="https://counter.theconversation.com/content/97900/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Charles MacRobert does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Can we trust expert football predictions? Perhaps, but it’s variable.Charles MacRobert, Lecturer in Civil Engineering, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/936922018-03-22T10:40:28Z2018-03-22T10:40:28ZHow do forensic engineers investigate bridge collapses, like the one in Miami?<figure><img src="https://images.theconversation.com/files/211423/original/file-20180321-165577-sf1q0z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What caused this bridge to collapse?</span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/University-Bridge-Collapse/102432490fb04a668e2c9baa1029a2de/11/1">AP Photo/Wilfredo Lee</a></span></figcaption></figure><p>On March 15, a 950-ton partially assembled pedestrian bridge at Florida International University in Miami <a href="http://www.miamiherald.com/news/local/community/miami-dade/west-miami-dade/article205316174.html">suddenly collapsed</a> onto the busy highway below, killing six people and seriously injuring nine. Forensic engineers are taking center stage in the ongoing investigation to find out what happened and why – and, crucially, to learn how to prevent similar tragedies in the future.</p>
<p>I’m not actively involved in this investigation, but I’ve been a forensic engineer for nearly 20 years and am the 2018 president of the <a href="http://www.nafe.org">National Academy of Forensic Engineers</a>. Similar to forensic scientists, we visit scenes of disasters and crimes to determine what role engineering practices played in what happened. The first step in any forensic investigation, collecting evidence, often can’t begin until <a href="https://www.cnn.com/2018/03/18/us/florida-bridge-collapse/index.html">survivors are rescued and victims are recovered</a>. Those operations displace material and can damage evidence, which means forensic engineers must study the emergency response as well, to be able to tell whether, for instance, a support column collapsed during the event or was destroyed to reach a victim in need of help. During the FIU recovery efforts rescuers used <a href="http://www.miamiherald.com/news/local/community/miami-dade/article205461214.html">large equipment to break up massive blocks of concrete</a> so that victims’ bodies could be recovered.</p>
<p>In Miami at the moment, forensic engineers and technicians from the <a href="http://www.ntsb.gov">National Transportation Safety Board</a> are on the scene. Right now they’re collecting samples of materials from the bridge to test for their physical properties. They’re reviewing drawings and plans, and examining both industry standards and site engineers’ calculations to understand what was supposed to be built – to compare with what was actually constructed. They’ll look at photographs and videos of the collapse to identify the <a href="https://doi.org/10.1016/S0167-9457(96)00048-6">sequence of events</a> and <a href="http://www.photogrammetry.com">locations of key problems</a>. Of course, they’ll also talk to witnesses to find out what workers and passersby saw and heard around the time of its collapse.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/211421/original/file-20180321-165554-1en0ick.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/211421/original/file-20180321-165554-1en0ick.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211421/original/file-20180321-165554-1en0ick.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=421&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211421/original/file-20180321-165554-1en0ick.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=421&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211421/original/file-20180321-165554-1en0ick.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=421&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211421/original/file-20180321-165554-1en0ick.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=529&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211421/original/file-20180321-165554-1en0ick.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=529&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211421/original/file-20180321-165554-1en0ick.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=529&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Every element holds clues to what happened – including the cracks in the concrete and stress marks in the metal rods.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/University-Bridge-Collapse/5ad16f7759e845ffaa0c7a94053555cd/21/1">AP Photo/Wilfredo Lee</a></span>
</figcaption>
</figure>
<p>Then they’ll combine and analyze all that data and information to identify as clearly as possible what went wrong, in what order. Often there are many factors, each leading to or amplifying the next, that ultimately caused the disaster. Putting that puzzle together is a key part of the forensic engineer’s role.</p>
<h2>Weakness in partial structure</h2>
<p>The FIU bridge was being built using a method called “<a href="https://www.popsci.com/failed-florida-bridge-what-went-wrong">accelerated bridge construction</a>,” with <a href="http://www.miamiherald.com/news/local/article205951034.html">separate sections</a> that needed to be put together: The footings were installed beside the road and the span was built nearby and lifted into place just days before the collapse. In a plan like that, each piece must be able to withstand the forces acting on it as they’re all being put together. A weakness in one place can cause problems elsewhere, ultimately leading to catastrophe.</p>
<p>Two key elements of the bridge design, the <a href="https://www.washingtonpost.com/news/grade-point/wp/2018/03/15/new-pedestrian-bridge-collapses-at-florida-international-university-injuring-several/">tall center pylon and pipe supports</a>, were not yet in place when the structure collapsed. They hadn’t been scheduled to be added until later in the process – and the bridge wasn’t slated to open <a href="https://www.usatoday.com/story/news/2018/03/15/fiu-pedestrian-bridge-design/429978002/">until next year</a>, so it’s likely that the project’s designers and engineers expected the bridge segment to hold while construction continued.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/211429/original/file-20180321-165577-19wycvf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/211429/original/file-20180321-165577-19wycvf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/211429/original/file-20180321-165577-19wycvf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/211429/original/file-20180321-165577-19wycvf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/211429/original/file-20180321-165577-19wycvf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/211429/original/file-20180321-165577-19wycvf.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/211429/original/file-20180321-165577-19wycvf.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">An artist’s rendering of what the final bridge was supposed to look like.</span>
<span class="attribution"><a class="source" href="https://twitter.com/citysweetwater/status/860502994806345729">City of Sweetwater</a></span>
</figcaption>
</figure>
<p>Part of a forensic engineering evaluation will investigate whether that was a reasonable expectation, and whether those missing elements reduced the strength of what was there enough for it to collapse.</p>
<h2>Searching for clues</h2>
<p>There are some other publicly available clues, too, that shed light on avenues likely under investigation already. <a href="http://www.miamiherald.com/news/local/community/miami-dade/article205637539.html">Dashcam video of the bridge collapse</a> seems to indicate that the initial failure was very close to the north end of the structure. It has been reported that a couple of days before the collapse, a <a href="http://www.miamiherald.com/news/local/community/miami-dade/article205627294.html">crack had been discovered</a> near the bridge’s north end. Additionally, the bridge span might have been either undergoing <a href="http://www.miaminewtimes.com/news/why-were-cars-under-fiu-bridge-stress-test-10179322">stress testing</a> or <a href="https://theconversation.com/how-would-engineers-build-the-golden-gate-bridge-today-77846">other adjustments</a> when it collapsed. It’s too early to say now – but the inquiry will certainly reveal – whether the crack and the stress testing put too much load at the north end of the bridge.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"975128710247481345"}"></div></p>
<p>There will be other questions too, like “<a href="https://www.usatoday.com/story/news/2018/03/15/fiu-pedestrian-bridge-design/429978002/">Why didn’t they use temporary supports to shore up the bridge?</a>” There may be a perfectly sensible explanation: Perhaps the bridge was supposed to be strong enough to support itself, for example. Or maybe temporary supports would have created a traffic hazard on the road below.</p>
<p>Some of those questions will not be entirely engineering-related. For example, many are asking “<a href="http://www.miamiherald.com/news/business/article205626989.html">Why wasn’t the road closed?</a>” The Tamiami Trail was shut down for a few hours while the bridge span was <a href="https://news.fiu.edu/2018/03/first-of-its-kind-pedestrian-bridge-swings-into-place/120385">put in place</a>. But then it was reopened to cars – a decision that would have been informed by engineering, of course, but could also have been influenced by concerns about <a href="http://www.miamiherald.com/news/local/community/miami-dade/article205422719.html">public safety or traffic congestion</a>. </p>
<p>At the moment, many of the questions the public has are also being investigated by forensic engineers. Their goal is to ensure that eventually those questions are all answered, and many more as well, about designs, materials, processes, procedures and safety precautions. Those lessons will inform not just any replacement for this particular bridge in Miami but future bridge construction projects elsewhere in the country and around the world, as the rest of the engineering community takes lessons from whatever the investigation uncovers, so builders can avoid similar mistakes – and tragedies. In a sense, it is fortunate that one of the <a href="https://abc-utc.fiu.edu/">leading centers</a> for accelerated bridge construction is right on the FIU campus.</p><img src="https://counter.theconversation.com/content/93692/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Martin Gordon receives funding from the US Department of Transportation. He is the 2018 President of the The National Academy of Forensic Engineers. </span></em></p>When structures collapse, what’s involved in finding out what really happened?Martin Gordon, Professor of Manufacturing and Mechanical Engineering Technology, Rochester Institute of TechnologyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/903752018-01-20T01:56:53Z2018-01-20T01:56:53ZFungi can help concrete heal its own cracks<figure><img src="https://images.theconversation.com/files/202606/original/file-20180119-80165-16n4l1t.jpg?ixlib=rb-1.1.0&rect=73%2C9%2C2819%2C1936&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Could a secret ingredient make crumbling concrete a thing of the past?</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/8867046@N07/5055582945">m_e_mccarron</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span></figcaption></figure><p>Infrastructure supports and facilitates our daily lives – think of the roads we drive on, the bridges and tunnels that help transport people and freight, the office buildings where we work and the dams that provide the water we drink. But it’s no secret that American infrastructure is <a href="http://www.infrastructurereportcard.org">aging and in desperate need of rehabilitation</a>.</p>
<p>Concrete structures, in particular, suffer from serious deterioration. Cracks are very common due to various chemical and physical phenomena that occur during everyday use. Concrete shrinks as it dries, which can cause cracks. It can crack when there’s movement underneath or thanks to freeze/thaw cycles over the course of the seasons. Simply putting too much weight on it can cause fractures. Even worse, the steel bars embedded in concrete as reinforcement can corrode over time.</p>
<p>Very tiny cracks can be quite harmful because they provide an easy route in for liquids and gasses – and the harmful substances they might contain. For instance, micro-cracks can allow water and oxygen to infiltrate and then corrode the steel, leading to structural failure. Even a slender breach just the width of a hair can allow enough water in to undermine the concrete’s integrity.</p>
<p>But continuous maintenance and repair work is difficult because it usually requires an enormous amount of labor and investment.</p>
<p>So since 2013, I’ve been trying to figure out how these harmful cracks could heal themselves without human intervention. The idea was originally inspired by the amazing ability of the human body to heal itself of cuts, bruises and broken bones. A person takes in nutrients which the body uses to produce new substitutes to heal damaged tissues. In the same way, can we provide necessary products to concrete to fill in cracks when damage happens?</p>
<p>My Binghamton University colleagues <a href="http://ws.binghamton.edu/me/Zhou/index.html">Guangwen Zhou</a> and <a href="http://www.binghamton.edu/centers/bbrc/daviddavies.html">David Davies</a>, <a href="http://plantbiology.rutgers.edu/faculty/zhang/Ning_Zhang.html">Ning Zhang</a> from Rutgers University and I have found <a href="https://doi.org/10.1016/j.conbuildmat.2017.12.233">an unusual candidate to help concrete heal itself</a>: a fungus called <em><a href="http://en.wikipedia.org/wiki/Trichoderma_reesei">Trichoderma reesei</a></em>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/202611/original/file-20180119-110113-1l6x51j.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/202611/original/file-20180119-110113-1l6x51j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/202611/original/file-20180119-110113-1l6x51j.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=487&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202611/original/file-20180119-110113-1l6x51j.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=487&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202611/original/file-20180119-110113-1l6x51j.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=487&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202611/original/file-20180119-110113-1l6x51j.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=612&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202611/original/file-20180119-110113-1l6x51j.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=612&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202611/original/file-20180119-110113-1l6x51j.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=612&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Researchers screened a number of fungi looking for a candidate that could help fill concrete cracks.</span>
<span class="attribution"><span class="source">Congrui Jin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We initially screened about 20 different species of fungi in order to find one that could withstand the harsh conditions in concrete. Some we isolated from the roots of plants that grew in nutrient-poor soils, including from the New Jersey Pine Barrens and the Canadian Rocky Mountains in Alberta.</p>
<p>We found that as calcium hydroxide from concrete dissolved in water, the pH of our fungal growth medium increased from a close-to-neutral original value of 6.5 all the way to a very alkaline 13.0. Of all the fungi we tested, only <em>T. reesei</em> could survive this environment. Despite the drastic pH increase, its spores germinated into threadlike hyphal mycelium and grew equally well with or without concrete.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/202652/original/file-20180120-110117-lxsl1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/202652/original/file-20180120-110117-lxsl1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/202652/original/file-20180120-110117-lxsl1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=456&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202652/original/file-20180120-110117-lxsl1a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=456&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202652/original/file-20180120-110117-lxsl1a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=456&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202652/original/file-20180120-110117-lxsl1a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=573&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202652/original/file-20180120-110117-lxsl1a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=573&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202652/original/file-20180120-110117-lxsl1a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=573&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Once the spores (left) germinate with the addition of water, they grow into threadlike hyphal mycelium (right).</span>
<span class="attribution"><span class="source">Congrui Jin</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We propose including fungal spores, together with nutrients, during the initial mixing process when building a new concrete structure. When the inevitable cracking occurs and water finds its way in, the dormant fungal spores will germinate.</p>
<p>As they grow, they’ll work as a catalyst within the calcium-rich conditions of the concrete to promote precipitation of calcium carbonate crystals. These mineral deposits can fill in the cracks. When the cracks are completely caulked and no more water can enter, the fungi will again form spores. If cracks form again and environmental conditions become favorable, the spores could wake up and repeat the process. </p>
<p><em>T. reesei</em> is eco-friendly and nonpathogenic, posing no known risk to human health. Despite its widespread presence in tropical soils, there are no reports of adverse effects in aquatic or terrestrial plants or animals. In fact, <em>T. reesei</em> has a long history of <a href="https://doi.org/10.1016/0168-1656(94)90126-0">safe use in industrial-scale production</a> of carbohydrase enzymes, such as cellulase, which plays an important role in fermentation processes during winemaking. Of course, researchers will need to conduct a thorough assessment to investigate any possible immediate and long-term effects on the environment and human health prior to its use as a healing agent in concrete infrastructure.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/202624/original/file-20180119-110084-1j62q4h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/202624/original/file-20180119-110084-1j62q4h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/202624/original/file-20180119-110084-1j62q4h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202624/original/file-20180119-110084-1j62q4h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202624/original/file-20180119-110084-1j62q4h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202624/original/file-20180119-110084-1j62q4h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202624/original/file-20180119-110084-1j62q4h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202624/original/file-20180119-110084-1j62q4h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Future cement recipes may include fungi.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/midtowncrossing/2999325087">Midtown Crossing at Turner Park</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>We still don’t fully understand this very young but promising biological repair technique. Concrete is a harsh environment for the fungus: very high pH values, relatively small pore sizes, severe moisture deficit, high temperatures in summer and low temperatures in winter, limited nutrient availability and possible exposure to ultraviolet rays from sunlight. All of these factors dramatically influence the fungi’s metabolic activities and make them vulnerable to death.</p>
<p>Our research is still in the initial stage and there’s a long way to go to make self-healing concrete practical and cost-effective. But the scope of American infrastructure’s challenges makes exploring creative solutions like this one worthwhile.</p><img src="https://counter.theconversation.com/content/90375/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Congrui Jin receives funding from the Research Foundation for the State University of New York’s Sustainable Community Transdisciplinary Area of Excellence Program.</span></em></p>Adding a bit of fungus to the initial ingredient list might be one way to endow concrete with the ability to fill in any bits of damage that occur, without the need for human intervention.Congrui Jin, Assistant Professor of Mechanical Engineering, Binghamton University, State University of New YorkLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/904092018-01-19T17:12:18Z2018-01-19T17:12:18ZBoris Johnson’s English Channel bridge: an engineering expert’s view<figure><img src="https://images.theconversation.com/files/202600/original/file-20180119-80176-l4js89.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/uk-south-coast-cliffs-view-top-618301010?src=ugigYRp3TSDh_tDSZcZn1Q-1-1">Shutterstock</a></span></figcaption></figure><p>Boris Johnson, the UK foreign secretary, <a href="http://www.bbc.com/news/uk-politics-42743909">has proposed</a> building a bridge across the English Channel to connect England and France, to complement the rail tunnel that opened in 1994. Leaving aside the political and financial challenge of such a project, would it even be feasible to build such a long structure over the open sea and one of the busiest shipping lanes in the world?</p>
<p>For spanning long distances we use either cable stayed or suspension bridges, because they are light compared to conventional bridges and provide large areas unobstructed by pylons.</p>
<p>The <a href="http://edition.cnn.com/travel/article/worlds-longest-bridges/index.html">longest suspension bridge</a> built to date is in Kobe, Japan, measuring 3.9 km in total, with clear space between its pylons of almost 2km.</p>
<p>The <a href="http://www.dailymail.co.uk/news/article-2343361/Worlds-longest-widest-cable-bridge-span-10km-finally-completed-seven-years-China-course.html">longest bridge with a single cable-stayed span</a> built to date is the Sutong Yangtze River Bridge near Suzhou, China. Its two pylons are separated by a 1km main span and it is 8km long in total. But it is not a completely suspended structure, with a number of densely spaced pylons on either side of the main span.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/202602/original/file-20180119-80206-cq8mea.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/202602/original/file-20180119-80206-cq8mea.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/202602/original/file-20180119-80206-cq8mea.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/202602/original/file-20180119-80206-cq8mea.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/202602/original/file-20180119-80206-cq8mea.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/202602/original/file-20180119-80206-cq8mea.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/202602/original/file-20180119-80206-cq8mea.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Sutong Bridge.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/download/confirm/682862707?src=ejZzwv7Lo7X7eyaLYZqesQ-1-0&size=huge_jpg">Shutterstock</a></span>
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</figure>
<p>Similarly, the <a href="http://www.dailymail.co.uk/news/article-2343361/Worlds-longest-widest-cable-bridge-span-10km-finally-completed-seven-years-China-course.html">longest bridge in the world</a> is the Danyang–Kunshan Grand Bridge in China. It is mostly a conventional bridge made from columns sunk into the seabed, although it has a cable-stayed section. The bridge is 165km long (just over 100 miles) but the short distance between the columns would not do for the busy Channel. </p>
<p>A bridge over the English Channel that wouldn’t disrupt shipping would require a span of 22 miles, or 38km in total, which is an order of magnitude larger than anything else built to date. This presents a considerable civil engineering challenge for a number of reasons.</p>
<h2>Tallest bridge ever</h2>
<p>The channel is between 40m and 60m deep and some passenger ships are <a href="https://www.marineinsight.com/know-more/top-10-largest-cruise-ships-2017/">more than 70m tall</a>. So to let ships pass underneath, the pylons supporting the bridge would have to be around 150m tall. To support the cables you would have to add pylons above the deck, which would mean a total pylon height well above 500m. Again, nothing this tall has ever been built.</p>
<p>Apart from the challenge of building them, the high pylons would need a very careful assessment of how the wind would affect them and the attached cables. This would have to be supported by a vibrational analysis to prevent potential failure. As the wind hits the pylons and the cables, it causes them to vibrate. In some instances, this can grow into a phenomenon known as “flutter”, causing the entire structure to become unstable, as happened to <a href="https://www.aps.org/publications/apsnews/201611/physicshistory.cfm">the Tacoma bridge</a>, which collapsed in 1940.</p>
<p>To prevent the cables from becoming overstressed, you would need a relatively large number of pylons to hold the bridge up. But again, this conflicts with the requirement of having unobstructed space on the water for ships to pass through.</p>
<p>The cables would also have to be very strong and light cables, possibly stronger than the very expensive carbon fibre composites. To make them we would probably need to research new materials and find a way to make it affordable.</p>
<p>Another big unknown quantity is the undersea ground conditions, which would need to be carefully investigated to see if they would be suitable for the pylons’ foundations. This means we also don’t know how much the foundations would add to the cost. </p>
<h2>Possible solution</h2>
<p>Following the lead of the Danyang–Kunshan Grand Bridge in China, it may be possible to combine a cable-supported structure, for the part where a clear sailing space is needed, with a conventional column bridge style. This might ease problems of construction and cost, although it may still disrupt shipping routes to a certain degree.</p>
<p>But the only thing we can say for sure is that cost of the project would likely run into billions of pounds. It’s a project that would require a lot of further research into the properties of cable materials, not to mention a proper feasibility study.</p><img src="https://counter.theconversation.com/content/90409/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Wanda Lewis does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>We’d need some major innovation to bridge the Channel without disrupting shipping.Wanda Lewis, Emeritus Professor, Civil Engineering, University of WarwickLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/781642017-07-28T12:38:48Z2017-07-28T12:38:48ZMeasuring up US infrastructure against other countries<figure><img src="https://images.theconversation.com/files/179649/original/file-20170725-30167-c4z100.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Heavy storms in February caused parts of a California highway to give way.</span> <span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Aging-Infrastructure-No-Quick-Fix/ffbd4acc4d7f49c9ab83e2784040b980/2/0">Rich Pedroncelli/AP Photo</a></span></figcaption></figure><p>How does infrastructure in the U.S. compare to that of the rest of the world? It depends on who you ask. </p>
<p>On the last two <a href="https://www.infrastructurereportcard.org/">report cards from the American Society of Civil Engineers</a>, U.S. infrastructure scored a D+. This year’s report urged the government and private sector to increase spending by US$2 trillion within the next 10 years, in order to improve not only the physical infrastructure, but the country’s economy overall.</p>
<p>Meanwhile, the country’s international rank in overall infrastructure quality jumped from 25th to 12th place out of 138 countries, according to the <a href="https://www.weforum.org/reports/the-global-competitiveness-report-2016-2017-1">World Economic Forum</a>.</p>
<p>On Feb. 12, the White House revealed <a href="http://abcnews.go.com/Politics/white-house-plan-calls-15-trillion-investments-fix/story">its $1.5 trillion plan</a> to rebuild U.S. infrastructure, financed through a combination of federal, local and private sectors. This is a long awaited plan, as the nation’s infrastructure quality continues to suffer. </p>
<p>The quality of infrastructure systems can be measured in different ways – including efficiency, safety and how much money is being invested. As a researcher in risk and resilience of infrastructure systems, I know that infrastructure assessment is far too complex to boil down into one metric. For instance, while the U.S. <a href="http://stats.oecd.org/#">ranks second in road infrastructure spending</a>, it falls in <a href="http://apps.who.int/gho/data/node.main.A997">60th place for road safety</a>, due to the high rate of deaths from road traffic. </p>
<p>But by many measures, the U.S. falls short of the rest of the world. Two of these characteristics are key to our infrastructure’s future: resilience and sustainability. A new class of solutions is emerging that, with the right funding, can help address these deficiencies.</p>
<h1>Resilience</h1>
<p>Resilient infrastructures are able to effectively respond to and recover from disruptive events. The U.S. is still in the top 25 percent of countries with the most resilient infrastructure systems. But it falls behind many other developed countries because the country’s infrastructure is aging and increasingly vulnerable to disruptive events. </p>
<p>For example, the nation’s inland waterway infrastructure has not been updated since it was first built in the 1950s. As a result, 70 percent of the 90,580 dams in the U.S. will be <a href="https://www.infrastructurereportcard.org/cat-item/dams/">over 50 years old by 2025</a>, which is beyond the average lifespan of dams. </p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/179629/original/file-20170725-26586-19dq7cm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179629/original/file-20170725-26586-19dq7cm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/179629/original/file-20170725-26586-19dq7cm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=440&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179629/original/file-20170725-26586-19dq7cm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=440&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179629/original/file-20170725-26586-19dq7cm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=440&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179629/original/file-20170725-26586-19dq7cm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=552&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179629/original/file-20170725-26586-19dq7cm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=552&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179629/original/file-20170725-26586-19dq7cm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=552&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Vehicles at a business are surrounded by floodwaters from 2016’s Hurricane Matthew in Lumberton, North Carolina.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/APTOPIX-Hurricane-Matthew-North-Carolina/bdf13182ee1340749c120ac252244386/69/1">AP Photo/Chuck Burton</a></span>
</figcaption>
</figure>
<p>In addition, since the 1980s, weather-related power outages in the U.S. have become as much as <a href="https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_b_1">10 times more frequent</a>.</p>
<p>Several European countries – such as Switzerland, Germany, Norway and Finland – are ahead of the U.S. in the <a href="http://www.fmglobal.com/research-and-resources/tools-and-resources/resilienceindex/explore-the-data/">FM Global Resilience Index</a>, a data-driven indicator of a country’s ability to respond to and recover from disruptive events. Though these countries are exposed to natural hazards and cyber risks, their infrastructure’s stability and overall high standards allow them to effectively survive disruptive events.</p>
<p>The U.S. infrastructure was built according to high standards 50 years ago, but that’s no longer enough to ensure protection from today’s extreme weather. Such weather events are becoming <a href="https://www.infrastructurereportcard.org/cat-item/dams/">more frequent and more extreme</a>. That has a severe impact on our infrastructure, as cascading failures through interdependent systems such as transportation, energy and water will ultimately adversely impact our economy and society.</p>
<p>Take 2016’s Hurricane Matthew, which was considered a <a href="http://www.nws.noaa.gov/ohd/hdsc/aep_storm_analysis/AEP_HurricaneMatthew_October2016.pdf">1,000-year flood event</a>. The unexpectedly strong rainfalls broke records and caused damages equivalent to <a href="https://www.ncdc.noaa.gov/billions/">$15 billion</a>. A better infrastructure that is modernized and well-maintained based on data-driven predictions of such events would have resulted in less impact and faster recovery, saving the society large damages and losses. </p>
<p>As the country’s infrastructure ages, extreme weather events have a greater impact. That means the recovery is slower and less efficient, making the U.S. less resilient than its counterparts.</p>
<h1>Sustainability</h1>
<p>In terms of sustainability practices designed to reduce impact on human health and the environment, the U.S. does not make it to <a href="http://www.robecosam.com/images/Country_Ranking_Update_October_2016.pdf">the top 10</a>, according to RobecoSAM, an investment specialist focused exclusively on sustainability investing. </p>
<p>Average CO₂ emissions per capita in the U.S. are double that of other industrialized countries and more than three times as high as those in France. </p>
<p>The infrastructure in most EU countries facilitates and encourages sustainable practices. For example, railroads are mostly dedicated to commuters, while <a href="http://business.tenntom.org/why-use-the-waterway/shipping-comparisons">the bulk of freight moves through waterways</a>, which is considered the most cost-effective and fuel-efficient mode of transportation.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/179651/original/file-20170725-30103-1ikjgjj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179651/original/file-20170725-30103-1ikjgjj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/179651/original/file-20170725-30103-1ikjgjj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179651/original/file-20170725-30103-1ikjgjj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179651/original/file-20170725-30103-1ikjgjj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179651/original/file-20170725-30103-1ikjgjj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179651/original/file-20170725-30103-1ikjgjj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179651/original/file-20170725-30103-1ikjgjj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In the U.S., 76 percent of commuters drive their own cars.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Watchf-AP-A-CA-USA-APHS272586-Los-Angeles-Eveni-/8f8e7dbfd3174e9c870f1781d0b9e0f4/41/0">Reed Saxon/AP Photo</a></span>
</figcaption>
</figure>
<p>In the U.S., however, 76 percent of commuters drive their own cars, as railroads are mostly reserved for freight and public transit is not efficient compared to other countries. American cities do not show up in the <a href="http://www.jll.com/Research/jll-business-of-cities-report-april-2016.pdf">top cities for internal transportation</a>, as do cities such as Madrid, Hong Kong, Seoul and Vienna. </p>
<p>To promote sustainable practices, global initiatives such as the <a href="http://newclimateeconomy.report/">New Climate Economy</a> and the <a href="http://www.hillcountryalliance.org/uploads/HCA/PlanningInfrastructure.pdf">Task Committee on Planning for Sustainable Infrastructure</a> aim to guide governments and businesses toward sustainable decision-making, especially when planning new infrastructure. </p>
<h1>Smart infrastructure as a solution</h1>
<p>To address challenges of resilience and sustainability, future infrastructure systems will have to embrace cyber-physical technologies and data-driven approaches. </p>
<p>A smart city is a city that is efficient in providing services and managing assets using information and communication technology. For example, <a href="https://www.technologyreview.com/s/532511/barcelonas-smart-city-ecosystem/">in Barcelona</a>, a city park uses sensor technology to collect and transmit real-time data that can inform gardeners on plant needs.</p>
<p>While there is no official benchmark to grade countries in this aspect, a number of American cities, such as <a href="http://www.govtech.com/Obama-Places-160-Million-Bet-on-Smart-Cities-Internet-of-Things.html">Houston and Seattle</a>, are considered among the world’s “smartest” cities, according to economic and environmental factors. </p>
<p>In order to prioritize dam restoration, the dam safety engineering practice is moving toward a data-driven process that would rank the dams based on how important they are to the rest of the waterway system. And last year, the U.S. Department of Transportation issued <a href="https://www.transportation.gov/briefing-room/traffic-fatalities-sharply-2015">a call to action</a> to improve road safety by releasing a large database on road fatalities, which researchers can study to answer important questions.</p>
<p>Similarly, worldwide initiatives are seeking smart solutions that integrate communication and information technology to improve the resilience of cities such as <a href="http://www.100resilientcities.org/">100 Resilient Cities</a> and <a href="http://www.smartresilience.eu-vri.eu/">Smart Resilience</a>. </p>
<p>It’s imperative that we pursue these types of new solutions, so U.S. infrastructure can better and more sustainably withstand future disruptions and deliver better quality of life to citizens, too. Perhaps, by addressing these needs, the U.S. can improve its score on its next report cards. </p>
<p><em>This is an updated version of an article originally published on July 28, 2017.</em></p><img src="https://counter.theconversation.com/content/78164/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hiba Baroud receives funding from the National Science Foundation, the Tennessee Department of Transportation, the Department of Transportation, and the U.S. Army Corps of Engineers. She is a member of the American Society of Civil Engineers, the Society for Risk Analysis, and the Institute for Operations Research and the Management Sciences.</span></em></p>The American Society of Civil Engineers gives US infrastructure a D+. What is it that we’re doing wrong?Hiba Baroud, Assistant Professor of Civil and Environmental Engineering, Vanderbilt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/778462017-05-26T21:34:37Z2017-05-26T21:34:37ZHow would engineers build the Golden Gate Bridge today?<figure><img src="https://images.theconversation.com/files/171209/original/file-20170526-6421-1j3azw3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What could be better?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/golden-gate-bridge-after-sunset-518608999">Uladzik Kryhin via Shutterstock.com.</a></span></figcaption></figure><p>Ever since the Golden Gate Bridge opened to traffic on May 27, 1937, it’s been an iconic symbol on the American landscape. </p>
<p>By 1870, people had realized the necessity of building a bridge spanning the Golden Gate Strait to connect the city of San Francisco with Marin County. However, it was another half-century before structural engineer Joseph Strauss submitted his bridge proposal. The plans evolved, and the final project was approved as a suspension bridge that ended up taking <a href="http://www.history.com/this-day-in-history/golden-gate-bridge-is-born">over four years to build</a>.</p>
<p>When the Golden Gate Bridge went up, it was the longest suspended bridge span in the world – cables hold up the roadway between two towers, with no intermediate supports. And the setting had a number of inherent challenges. It cost about <a href="http://goldengatebridge.org/research/ConstructionPrimeContr.php">US$37 million</a> at the time; building the same structure today would cost about a billion dollars. So how has the design held up over the past 80 years – and would we do things differently if we were starting from scratch today?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171196/original/file-20170526-6402-sshvmr.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171196/original/file-20170526-6402-sshvmr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171196/original/file-20170526-6402-sshvmr.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=164&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171196/original/file-20170526-6402-sshvmr.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=164&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171196/original/file-20170526-6402-sshvmr.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=164&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171196/original/file-20170526-6402-sshvmr.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=205&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171196/original/file-20170526-6402-sshvmr.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=205&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171196/original/file-20170526-6402-sshvmr.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=205&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Schematic of a suspension bridge. The red supporting cables transfer forces from the black suspending cables to the blue towers and anchors.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Bridge-suspension.svg">The Conversation</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Longest suspension bridge in the world</h2>
<p>The Golden Gate Bridge is a suspension bridge, meaning it relies on cables and suspenders under tension along with towers under compression to cross a long distance without any intermediate supports. The roadway deck hangs from vertical suspenders that connect to the two main cables that run between the towers and the anchors on the end. The suspenders transfer vehicular forces and self-weight to the supporting cables that are anchored to towers and on to solid ground.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/171186/original/file-20170526-6408-y310ow.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171186/original/file-20170526-6408-y310ow.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/171186/original/file-20170526-6408-y310ow.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=394&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171186/original/file-20170526-6408-y310ow.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=394&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171186/original/file-20170526-6408-y310ow.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=394&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171186/original/file-20170526-6408-y310ow.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=495&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171186/original/file-20170526-6408-y310ow.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=495&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171186/original/file-20170526-6408-y310ow.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=495&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A simple woven suspension bridge.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:IRB-6-BringingDeckMat-KC603-8.jpg">Rutahsa Adventures</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>The <a href="https://extendedprojectelodie.wordpress.com/2012/11/04/history-of-suspension-bridges/">first bridges of this type</a> probably connected two cliffs with flexible ropes to cross a valley or a river. Hundreds of years ago, these ropes were made of plant fiber; iron chains came later. The Brooklyn Bridge in New York City, opened in 1883, was the first to use steel cables, which then became standard.</p>
<p>The towers likely started as a simple rock on each side of a valley; eventually engineers used massive stone or steel piers. The Golden Gate Bridge, for instance, is supported by one abutment on each end and the two towers, which are placed over foundations embedded in the seafloor.</p>
<p>The Golden Gate Bridge’s two supporting cables are about the only thing that has not been changed since the bridge was opened to traffic in 1937. Each main cable is formed by 27,572 steel wires with the approximate thickness of a pencil. Construction crews hung nearly <a href="http://goldengatebridge.org/research/factsGGBDesign.php">80,000 miles of wire cables</a> from one side of the bridge to the other. </p>
<p>It’s nearly impossible to manufacture a long, thick cable in one piece with no flaws to do this job. And crucially, if a single big cable was holding the bridge up and something happened to it, there would be a catastrophic failure. Relying on smaller wires means any failure would be slower, leaving time to divert disaster. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171188/original/file-20170526-6371-t4lg76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171188/original/file-20170526-6371-t4lg76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171188/original/file-20170526-6371-t4lg76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=442&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171188/original/file-20170526-6371-t4lg76.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=442&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171188/original/file-20170526-6371-t4lg76.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=442&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171188/original/file-20170526-6371-t4lg76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=555&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171188/original/file-20170526-6371-t4lg76.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=555&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171188/original/file-20170526-6371-t4lg76.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=555&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Workers during construction of the bridge, circa 1935.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/7552532@N07/4474077027/">ATOMIC Hot Links</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Since people first started pondering a bridge in the bay of San Francisco, there was huge concern about the structure’s ability to withstand the location’s strong winds, turbulent waters and possible earthquake forces. San Francisco is located at the intersection of two <a href="http://www.sfnps.org/geology">active tectonic plates</a> – obviously no one wanted to see an earthquake bring down the bridge, which currently carries around <a href="http://goldengatebridge.org/tolls_traffic/">112,000 vehicles per day</a>.</p>
<p>To avoid this problem, the builders also located shock absorbers at each end of the bridge to absorb the energy coming from wind or seismic forces. These specially designed vibration dampers are meter-diameter cylinders made of a lead core covered by rubber. Placed at strategic locations, they absorb energy that could otherwise cause the bridge to collapse. </p>
<h2>Keeping it in good shape</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/171189/original/file-20170526-6402-1s65n9i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171189/original/file-20170526-6402-1s65n9i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/171189/original/file-20170526-6402-1s65n9i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=909&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171189/original/file-20170526-6402-1s65n9i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=909&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171189/original/file-20170526-6402-1s65n9i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=909&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171189/original/file-20170526-6402-1s65n9i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1142&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171189/original/file-20170526-6402-1s65n9i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1142&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171189/original/file-20170526-6402-1s65n9i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1142&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Workers vigilantly monitor and maintain the bridge.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/mischiru/2074892499">Kevin Lau</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Conventional wisdom would suggest an infrastructure project is done soon after its inauguration. But keeping the Golden Gate Bridge in tiptop form requires ongoing stringent maintenance. For 80 years, <a href="http://goldengatebridge.org/research/caretakers.php">dedicated maintenance crews</a> have serviced the bridge, repainting and substituting the corroded or broken components where necessary.</p>
<p>This work must be done to exacting standards. For example, when any of the thousands of bolts that connect all the various pieces of the bridge need replacement, no more than two are taken out simultaneously, to keep the bridge safe against strong winds or earthquakes forces. </p>
<p>There are structural maintenance issues, too. Due to the passage of time and ongoing temperature variability, the cables and suspenders elongate or contract, and need periodical checking and retensioning. This type of adjustment is referred to as “tuning” and is similar to how a musician keeps a stringed instrument sounding its best.</p>
<h2>What would change if we built it today?</h2>
<p>Due to huge <a href="https://www.johndcook.com/blog/2010/03/31/maintenance-costs/">upkeep costs</a>, some people have suggested reconstructing the Golden Gate Bridge in a way that would limit ongoing maintenance and operation bills. Setting aside the political feasibility, how would engineers design the bridge if they were going to build it from scratch today?</p>
<p>Over time, researchers have developed lighter materials. Using Fiber Reinforced Polymers (FRPs) rather than steel or concrete is a way to reduce the weight of a structure of this magnitude. This self-weight is typically responsible for using up 70 to 80 percent of its resistence – that’s the maximum load it can bear before it fails. By reducing it, the bridge’s structure would need less strength, allowing for cheaper and easier options.</p>
<p>For example, designers have started using Fiber Reinforced Composite (FRP) materials in bridges such as the Market Street Bridge in West Virginia. FRP uses a plastic resin to bind together glass or carbon fibers, which give strength to the material. Being four times lighter than concrete, the FRPs are five to six times stronger.</p>
<p>Probably a designer’s first target for change in a substitute Golden Gate Bridge would be the composition of the cables. The steel currently in use is corrosive, heavier by four times than newer materials and can fail in harsh moisture and temperature environments – just like those it encounters in this location. Carbon cables are more inert and already in use around the world. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/171197/original/file-20170526-6415-1qyqryg.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/171197/original/file-20170526-6415-1qyqryg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/171197/original/file-20170526-6415-1qyqryg.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=164&fit=crop&dpr=1 600w, https://images.theconversation.com/files/171197/original/file-20170526-6415-1qyqryg.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=164&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/171197/original/file-20170526-6415-1qyqryg.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=164&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/171197/original/file-20170526-6415-1qyqryg.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=205&fit=crop&dpr=1 754w, https://images.theconversation.com/files/171197/original/file-20170526-6415-1qyqryg.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=205&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/171197/original/file-20170526-6415-1qyqryg.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=205&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In a cable-stayed bridge, the cables connect directly from the deck to the towers.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Bridge-harp-cable-stayed.svg">The Conversation</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>These lighter-than-steel materials could also be utilized in other elements of the bridge, such as the traffic roadway. Using plastic composite decking could bring the Golden Gate Bridge’s deck self-weight down by a factor of five. That would enable engineers to design and construct a cable-stayed bridge rather than a suspension bridge. The advantage there would be the ability to do away with the suspenders; in a cable-stayed bridge forces are transmitted directly from the deck to the towers by the cables. The first highway cable-stayed bridge with CFRP cables is Switzerland’s Stork Bridge, opened in 1996. </p>
<p>A cable-stayed bridge can have a longer span than a suspension bridge, so its structure between the supports and the shore could be simpler. Also building the towers nearer to the shore, where the waterbed is more shallow, would help alleviate one of the main problems when the Golden Gate Bridge was constructed the first time around: It’s very difficult and expensive to work on the tower foundations in deep water with strong currents.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/XggxeuFDaDU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Collapse of the Tacoma Narrows Bridge.</span></figcaption>
</figure>
<p>The damping system could also be addressed with a new design. The lead core-based dampers that were used in the construction of the Golden Gate could be replaced by newer technologies that are better able to resist wind, traffic and seismic forces. This improvement would ensure that a failure such as the one on the Tacoma Narrows Bridge – when wind blew the bridge sideways, it twisted and collapsed – would be prevented.</p>
<p>With all that said, the Golden Gate Bridge is still doing fine. Even with other feasible and cheaper options, no one is realistically working to replace the Art Deco icon and its world famous “international orange” paint job. The Golden Gate Bridge is closely monitored to make sure it does not exceed its stress limits due to traffic, wind and seismic loads. We can look forward to at least another 80 years of this engineering masterpiece.</p><img src="https://counter.theconversation.com/content/77846/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hota GangaRao receives funding from NSF, USACE, WVDOT, LTRC, CreativePultrusions and USDOD.</span></em></p><p class="fine-print"><em><span>Maria Martinez de Lahidalga de Lorenzo does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s been 80 years since this beloved landmark opened to San Francisco traffic. In the interim, technology has advanced – is there a better way to span this strait?Hota GangaRao, Professor of Civil and Environmental Engineering, West Virginia UniversityMaria Martinez de Lahidalga de Lorenzo, Graduate Research Assistant, West Virginia UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/766122017-04-27T09:55:29Z2017-04-27T09:55:29ZThis fantastic idea for a circular runway is sadly going nowhere<figure><img src="https://images.theconversation.com/files/166586/original/file-20170425-12645-izov76.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">NLR/Endless Runway</span></span></figcaption></figure><p>Building a new runway is often a tight squeeze. For example, part of the opposition to a new runway in London, which has <a href="http://www.telegraph.co.uk/news/2016/10/15/tory-revolt-over-heathrow-third-runway-as-60-mps-oppose-plans-an/">provoked national debate</a>, comes from the hundreds of families whose <a href="http://www.bbc.co.uk/news/uk-england-37667371">homes will be demolished</a> to make way for the airport expansion. But a team of Dutch scientists have now come up with an airport design that would allow large numbers of aircraft to take off in a much smaller space than currently possible – by using a circular runway.</p>
<p>The <a href="http://www.endlessrunway-project.eu">researchers behind the Endless Runway project</a> from the Netherlands Aerospace Centre argue that it would allow aircraft to land and take off in any direction. This would reduce fuel costs and turbulence and sometimes even allow flights to take off when they would otherwise be delayed because they are waiting for a space on the runway. It could also help lower ticket prices and spread out noise pollution so it’s not concentrated over one narrow area.</p>
<p>As a retired airline captain, I admire the idea. It is a fantastic and thought-provoking notion. To the general public, it probably sounds too good to be true. And sadly, it is. Even if its designers were to solve all its problems and find a backer, it probably couldn’t come to fruition for decades.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/166944/original/file-20170427-15086-1u5o67h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166944/original/file-20170427-15086-1u5o67h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166944/original/file-20170427-15086-1u5o67h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166944/original/file-20170427-15086-1u5o67h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166944/original/file-20170427-15086-1u5o67h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166944/original/file-20170427-15086-1u5o67h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166944/original/file-20170427-15086-1u5o67h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fantastic idea, too good to be true.</span>
<span class="attribution"><span class="source">NLR</span></span>
</figcaption>
</figure>
<p>This idea was actually first proposed <a href="https://books.google.co.uk/books?id=_igDAAAAMBAJ&pg=PA73&lpg=PA73&dq=Would+This+Circular+Track+Solve+the+Landing+Problem?,+in+Popular+Science,+June+1919&source=bl&ots=KiK2l26cDN&sig=2odtgiRzXkg-_sJHNxDxQqeJitA&hl=en&sa=X&ved=0ahUKEwj4mNaJv8LTAhXKKcAKHU5-BbwQ6AEIJzAB#v=onepage&q&f=false">nearly a century ago, in 1919,</a> and was further <a href="https://www.aerosociety.com/news/would-circular-runways-drive-pilots-round-the-bend/">tested by the US Navy in the mid 1960s</a>. These trials were carried out at the General Motors circular and banked test track in Arizona and worked very well. But they were all completed on a smaller scale with much smaller aircraft, by pilots who were mostly accustomed to landing on an aircraft carrier.</p>
<p>They were flown in perfect weather conditions without the need for the inherent safety protections of the computer technology used in today’s aircraft landing systems. Crucially, the landings were done one at a time under test conditions, not every two minutes, day and night, from different directions, as a fully operating circular airport would require.</p>
<p>The bigger picture reveals there would be a succession of impediments to the success of this idea, particularly from the viewpoint of airport operators, air traffic control teams and pilots.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/166945/original/file-20170427-15121-8tqzwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166945/original/file-20170427-15121-8tqzwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166945/original/file-20170427-15121-8tqzwm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166945/original/file-20170427-15121-8tqzwm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166945/original/file-20170427-15121-8tqzwm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166945/original/file-20170427-15121-8tqzwm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166945/original/file-20170427-15121-8tqzwm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Recipe for chaos.</span>
<span class="attribution"><span class="source">NLR</span></span>
</figcaption>
</figure>
<p>Every runway has precise instructions for the approach and landing phase of a flight, which pilots must be able to follow on their instruments when in cloud or low visibility. Similarly, when taking off, pilots have to follow precise routes, partly to minimise noise pollution but mainly to keep them in a safe corridor, clear of any high ground. If aircraft could come from any direction and land as it suited them, there would be chaos.</p>
<p>What’s more, sometimes aircraft have to land or abandon their landing in an emergency. Aborting a circular landing could mean the aircraft flying off in potentially any direction, perhaps into oncoming traffic on another part of the circle, or even into a mountain. What you need is a singular safe option, just as we have now. </p>
<p>Today’s technology only allows for a selected number of arrival routes using the <a href="http://www.airservicesaustralia.com/projects/gold-coast-ils/what-is-an-instrument-landing-system/">autopilot-assisted instrument landing system</a> that transmits guidance signals from the runway to the aircraft. This automatically flies the aircraft down an unseen conveyor belt onto the start of the runway for manual landing, and will even automatically land the aircraft in thick fog. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/166946/original/file-20170427-15102-1cll39z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166946/original/file-20170427-15102-1cll39z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=271&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166946/original/file-20170427-15102-1cll39z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=271&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166946/original/file-20170427-15102-1cll39z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=271&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166946/original/file-20170427-15102-1cll39z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=341&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166946/original/file-20170427-15102-1cll39z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=341&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166946/original/file-20170427-15102-1cll39z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=341&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">New guidance systems needed.</span>
<span class="attribution"><span class="source">NLR</span></span>
</figcaption>
</figure>
<p>These systems are currently fixed in one position and can’t simply change the guidance for the aircraft to land in a different place. New guidance systems, known as Adaptive Runway Aiming Points, that could make it possible to reposition the landing point <a href="https://www.google.com/patents/US9014882">are being developed</a>. They are first small step towards the technological realisation of the circular runway.</p>
<p>However, it is not just a question of waiting for technology to catch up.<a href="http://gizmodo.com/a-beginners-guide-to-the-secret-language-of-airport-run-1689493625">Traditional runways at airports are full of symbols and lights to aid safety</a>. A circular airport could have aircraft landing in many different places, and indicating where one aircraft’s section of runway ended and another’s began would be impossible on a continuous runway.</p>
<h2>Changing conditions</h2>
<p>As the Dutch researchers note, take-offs and landings on regular runways can be made difficult by strong (but consistent) crosswinds. An aircraft could lift off from a circular runway in a direction where these crosswinds wouldn’t affect it, but there would only be two points on the circle where this was the case. On any long circular take-off or landing roll, there would be increasing and decreasing amounts of crosswind as the aircraft turns the corner.</p>
<p>What’s worse, the wind might change from one side of the aircraft to the other. The headwind component, which is used to calculate speeds for take-off, would also vary considerably as you moved round the circle. You would need a way to account for all these fluctuating circumstances.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/166947/original/file-20170427-15102-yud83e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/166947/original/file-20170427-15102-yud83e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/166947/original/file-20170427-15102-yud83e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/166947/original/file-20170427-15102-yud83e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/166947/original/file-20170427-15102-yud83e.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/166947/original/file-20170427-15102-yud83e.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/166947/original/file-20170427-15102-yud83e.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In for a bumpy landing.</span>
<span class="attribution"><span class="source">NLP</span></span>
</figcaption>
</figure>
<p>Finally, in order to land without scraping the wings or engines on a curving, banked runway, the pilot would have to be highly trained to transition from a stable, level approach to a <a href="https://www.aerosociety.com/news/would-circular-runways-drive-pilots-round-the-bend/">curving, banked movement</a>. Alternatively, the autopilot could, possibly, be redesigned to cope.</p>
<p>The challenge of developing a successful circular runway proposal would at least give aircraft manufacturers the advantage of time to implement new autopilot capabilities. They could further use this time to take up another of the Dutch researchers’ suggestions: a completely new fatter and wider aircraft design with the engines safely on top of the wings that would <a href="https://www.aerosociety.com/news/would-circular-runways-drive-pilots-round-the-bend/">better suit the new runway design</a>. At the moment, such a design does not exist at all.</p>
<p>A circular runway fits nicely with the kind of artists’ impressions of the future that show a space age 21st century full of self-driving hovercars and holidays on the Moon. And, in fairness, prototypes of these other technologies are already being developed. But until we overcome the inertia of the aircraft industry, find improbable investment and unimaginable political will, circular runways will sadly remain just a vision.</p><img src="https://counter.theconversation.com/content/76612/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Lindsay Cole does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A round airport would let more flights take off in a smaller space, but the technology is nowhere near ready to make it work.Lindsay Cole, Lecturer in Tourism, Edinburgh Napier UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/756642017-04-04T14:50:18Z2017-04-04T14:50:18ZHow science can help cities prepare for attacks on metro systems<figure><img src="https://images.theconversation.com/files/163844/original/image-20170404-5702-ctctxt.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Tokyo, Moscow, Madrid, London, Brussels, and now St Petersburg. These major cities have all suffered attacks on their metro systems. The most recent events in St Petersburg, where a metro bombing <a href="http://www.bbc.co.uk/news/world-europe-39486640">killed at least 14 people</a>, remind us of the challenges faced by underground transport systems in keeping people safe during an emergency. This is where engineering and psychology research can come in useful, helping to optimise evacuation procedures using insight into how people behave.</p>
<p>To start with, there are several key ways that evacuating an underground system differs from evacuating a building. Underground environments are often unfamiliar to the evacuees, especially if the evacuation has to start in the tunnels between stations. The system’s enclosed nature also means visibility can rapidly deteriorate from smoke. Tunnels are generally not divided into separate sections to stop smoke spreading, which allows it to rapidly fill all spaces.</p>
<p>This can cause a number of problems when it comes to evacuating passengers. <a href="https://lup.lub.lu.se/search/publication/8033733">Evacuation slows down</a> when visibility is poor and people cannot fully rely on what they can see to help them get out. Smoke can also obscure signs and other visual instructions, making it difficult for people to locate the closest emergency exit. For this reason, evacuees often rely on alternative senses such as hearing or touch to find their way to safety. This is why auditory alarms and hand rails can be <a href="http://www.sciencedirect.com/science/article/pii/S0379711213000660">much more useful</a>.</p>
<p>Another reason these kind of guides and information are needed is because people tend to <a href="http://www.sciencedirect.com/science/article/pii/0925753596810113">move towards familiar places</a> or people in an emergency. For example, if someone is looking for a way out of a metro system, they may well try to get back to where they came in. But in many instances, closer emergency exits may be available in the tunnels. These exits often lead to safety in a significantly shorter time.</p>
<p>Similarly, people’s attention can narrow to focus on immediate threats rather than analysing all the information available to them, especially when they are under pressure to escape as quickly as possible. This is where social influence can come in. If one person can find a quicker evacuation route, their interaction with other evacuees can help spread this information and <a href="http://www.sciencedirect.com/science/article/pii/S1369847814000771">help everyone get out quicker</a>.</p>
<p>At a more fundamental level, the design of the tunnels and trains can lead to significant safety improvements. <a href="http://www.sciencedirect.com/science/article/pii/S0925753513002336">Experimental research</a> has shown the effectiveness of an evacuation from a metro train depends on the configuration of the train door and the space available after getting out of it. This can include the presence of a height gap between the train doors and the outside floor and narrow spaces for evacuation in the tunnels.</p>
<p>The height gap in particular, which can be up to 1.4 metres, can be a major obstacle during evacuation, slowing down the flow of people out of the train. It may also mean that some evacuees, particularly children and older people, may not be able to evacuate on their own. This height difference can make it even more important that the driver manages to get the train to a station, as the driver in the <a href="http://edition.cnn.com/2017/04/03/europe/st-petersburg-russia-explosion/">St Petersburg attack did</a> – despite the fact the bomb went off inside a tunnel. This likely led to a quicker evacuation and less severe consequences.</p>
<p>It’s worth also considering that people are often a lot <a href="http://onlinelibrary.wiley.com/store/10.1002/fam.1083/asset/fam1083.pdf?v=1&t=j13hxkr4&s=263c6c74e40c0ab28653b2c3da307c3d34187180">more rational than you might think</a> in a disaster. <a href="http://www.independent.co.uk/news/world/europe/st-petersburg-explosions-bomb-attack-witness-metro-victims-blasts-station-doors-a7664356.html">Media reports</a> often use the <a href="https://www.thesun.co.uk/news/3250916/st-petersburg-sennaya-ploshchad-metro-station-lockdown-bomb-threat/">ambiguous word “panic”</a>, suggesting irrational and competitive (anti-social) behaviour. But <a href="http://sro.sussex.ac.uk/13378/">investigations of disasters</a> have demonstrated that people actually tend to act rationally and in a non-competitive way.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/zuj8KT6Okco?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>In fact, people often tend to help each other in emergencies, including during <a href="http://link.springer.com/article/10.1007/s10694-015-0471-4">metro train evacuations</a>. For example, footage from the St Petersburg bombing shows people trying to help others get out of the attacked trains, and similar altruistic behaviours have <a href="https://www.nist.gov/publications/occupant-behavior-egress-and-emergency-communication-federal-building-and-fire-safety-0?pub_id=101046">been observed</a> in several <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.58.824&rep=rep1&type=pdf">other disasters</a>. So whatever preparations metro authorities make for disasters, they can consider their passengers to be part of their solution. They need to design the tunnel environment for the people, not the people for the environment.</p><img src="https://counter.theconversation.com/content/75664/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Enrico Ronchi receives funding from the Swedish Transport Administration and the German Federal Ministry of Education and Research.</span></em></p><p class="fine-print"><em><span>Daniel Nilsson receives funding from Brandforsk, Swedish Civil Contingencies Agency (MSB), Swedish Transport Administration and Norwegian Public Roads Administration.</span></em></p>The St Petersburg attack shows how engineering and psychology can help optimise how people are evacuated in a disaster.Enrico Ronchi, Associate Senior Lecturer in Evacuation Modelling, Lund UniversityDaniel Nilsson, Senior Lecturer, Lund UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/697482017-03-14T00:19:43Z2017-03-14T00:19:43ZUpgrading our infrastructure: Targeting repairs for locks, dams and bridges<figure><img src="https://images.theconversation.com/files/160608/original/image-20170313-9641-1r6ag14.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Maintenance work on Lock and Dam 8 on the Mississippi River near Genoa, Wisconsin.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/usacehq/12230736026/in/photolist-jCMHH5-e5UZFy-hyVkv3-6Ko6Nx-kMSBYV-94UKBU-dSEvdh-kMSvYD-kMTTh9-aneTyg-fEpDv5-kMSAkz-fvKeBw-ayZr5C-jCMrzJ-Rzb2eL-dK9A7z-pSAx18-ee5ihk-8F5fn5-aNKQQp-dBHnZV-f7Tzor-haCizS-pCdgLv-jCJMjP-84bwZr-9dC8ZQ-xeq9K2-d72DmA-ayWMeP-9gsTi7-bua96R-spNMkT-bqnR3W-anx33A-ac8Enb-bfNX2c-eeaZ4d-spF6fC-oUDn93-dB4DaE-8F567G-8F7rzG-kMSx4V-cCjHih-beqDtD-abPFyR-fmd4tB-kMRSm6">Patrick Moes, USACE/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>For the second time in a row, America’s infrastructure has <a href="http://www.infrastructurereportcard.org/">earned a grade of D+</a> from the American Society of Civil Engineers. ASCE issues these report cards every four years, grading the state of U.S. bridges, dams, parks, airports, railroads and other vital links. The fact that our nation’s overall grade has not improved since the last report card in 2013 shows that major investments are long overdue.</p>
<p>President Trump has promised to propose <a href="https://www.washingtonpost.com/business/economy/trump-activates-team-for-1-trillion-infrastructure-plan-but-challenges-mount/2017/03/08/ae57eaba-035e-11e7-b1e9-a05d3c21f7cf_story.html?utm_term=.e6357e5cc927">US$1 trillion in investments</a> over 10 years to modernize the nation’s infrastructure. If the Trump administration finds a way to fund such a plan, it will face many pressing questions over how to spend the money.</p>
<p>The most likely and logical strategy would be to pursue a combination of new construction projects, repairs and retrofits, selected to provide maximum bang for the buck. Repairing a structure is typically less expensive than retrofitting it by adding new components, which in turn is cheaper than building a new structure.</p>
<p>At Colorado State University (CSU) we are <a href="http://www.engr.colostate.edu/ce/academicprograms/structural.shtml">developing</a> two strategies that can prolong the service life of structures such as bridges and navigation locks. First, we are identifying appropriate intervals between inspections, to minimize inspection costs without undercutting public safety. Second, we are using innovative methods to effectively increase structures’ service lives, reducing the need for expensive new construction projects. </p>
<h2>Cracks in aging bridges</h2>
<p>The United States has <a href="http://www.infrastructurereportcard.org/cat-item/bridges/">614,837 bridges</a>, of which almost 40 percent are 50 years old or more. Since many were originally designed with 50-year service lives, it is not a surprise that they are degrading. According to ASCE, on average there were 188 million trips across structurally deficient bridges daily in 2016.</p>
<p>In steel bridges, localized structural damage produces a weakened condition that material scientists call fatigue. Cyclical loading from years of passing traffic then causes cracks to develop. Most older steel bridges suffer from fatigue and eventual cracking because codes in place when they were designed did not adequately address this problem, or because they are carrying loads heavier than they were originally designed to bear. </p>
<p>Fatigue crack growth generally can be managed through regular repairs without compromising the bridge’s performance. However, if cracks are not repaired, they can grow quickly, which could lead to catastrophic failure. This means it is critically important to quantify rates of crack growth, and to understand how rapid crack growth can affect the integrity of bridges. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/154314/original/image-20170125-23867-vwjnfc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/154314/original/image-20170125-23867-vwjnfc.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=452&fit=crop&dpr=1 600w, https://images.theconversation.com/files/154314/original/image-20170125-23867-vwjnfc.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=452&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/154314/original/image-20170125-23867-vwjnfc.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=452&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/154314/original/image-20170125-23867-vwjnfc.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=568&fit=crop&dpr=1 754w, https://images.theconversation.com/files/154314/original/image-20170125-23867-vwjnfc.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=568&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/154314/original/image-20170125-23867-vwjnfc.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=568&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Cracked cross girder-to-fascia stringer connection in a steel bridge.</span>
<span class="attribution"><span class="source">Hussam Mahmoud</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Which bridges should be repaired first?</h2>
<p>Some bridges are high priorities for inspection and repair because the <a href="http://www.transportation.org/">American Association of State Highway and Transportation Officials</a> classifies them as “fracture critical.” This means that they contain elements whose failure is expected to cause part or all of the bridge to collapse, because the bridge does not have other components that can support the weight.</p>
<p>The National Bridge Inspection Program was created after the <a href="http://www.transportation.wv.gov/highways/bridge_facts/Modern-Bridges/Pages/Silver.aspx">Point Pleasant Bridge</a> over the Ohio River collapsed in 1967, killing 46 people, when a single metal bar in a suspension chain failed. Standards were tightened after a 100-foot section of the <a href="https://www.ntsb.gov/investigations/AccidentReports/Pages/HAR8403.aspx">Mianus River Bridge</a> on Interstate 95 in Connecticut collapsed in 1983, killing three people. The collapse occurred after rusting caused an outer bearing to fail.</p>
<p>Most bridges built since the mid-1970s have redundant designs that can still support loads if a component fails. This means that a bridge may develop large cracks without risking a structural collapse. </p>
<p>At CSU we are using probabilistic evaluation and advanced 3D computer models to see how fatigue cracks grow in two-girder steel bridges and assess the potential for bridge collapse. (Girders are the horizontal beams or structures that support the deck of a bridge.) Two-girder bridges are critical targets, since only one girder will remain to support loads if the other fails.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/160360/original/image-20170310-19266-g2uze1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/160360/original/image-20170310-19266-g2uze1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/160360/original/image-20170310-19266-g2uze1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/160360/original/image-20170310-19266-g2uze1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/160360/original/image-20170310-19266-g2uze1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/160360/original/image-20170310-19266-g2uze1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/160360/original/image-20170310-19266-g2uze1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">New Pacific Avenue Bridge girders under construction in Tacoma, Washington.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/wsdot/26030979505">WSDOT/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
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<p>By quantifying how quickly cracks are growing, we can prescribe how frequently bridges should be inspected. This helps transportation agencies avoid either wasting money doing unnecessary inspections or allowing cracks to grow to a point that compromises bridge integrity.</p>
<p>These analyses have to account for many factors, such as uncertainties about the properties of bridge construction materials, the loads that bridges are supporting, and how well materials can resist a brittle fracture when a crack becomes very long. We carry out many simulations with numerous variations to account for these uncertainties. </p>
<p>One of our analyses showed that even when a bridge developed a crack in one of the girders that split the girder in two, the bridge was not at risk of total failure because other bridge components carried the load and were not at risk of breaking. This result suggests that stringent requirements for frequent inspection of two-girder bridges may be overkill. Of course, this conclusion cannot be generalized. Engineers should conduct other studies on a case-by-case basis to investigate ways in which load is redistributed and transferred to the other girder once one girder develops such a significant crack.</p>
<p>Currently there is no specific methodology in place to help engineers prioritize which crack to repair in which bridge and how frequently repairs should be made. But once we understand how fast and where major cracks develop, we can intervene at the right time to prolong a structure’s service life by delaying or even arresting the growth of fatigue cracks. </p>
<h2>Better retrofits</h2>
<p>Our program is also developing effective retrofit methods for mitigating fatigue crack growth in steel structures, focusing on navigation facilities such as locks and dams. ASCE gave the nation’s 25,000 miles of inland waterways and 239 locks <a href="http://www.infrastructurereportcard.org/cat-item/inland-waterways/">a grade of D</a>, noting that most locks and dams on the system are well past their 50-year design lives. </p>
<p>Currently we are carrying out studies for the <a href="http://www.usace.army.mil/">U.S. Army Corps of Engineers</a>, which manages major inland waterways, to evaluate the use of carbon fiber reinforced polymer (CFRP) composites for rapid and effect retrofits to mitigate underwater fatigue cracking in <a href="http://library.water-resources.us/docs/MMDL/FLD/Feature.cfm?ID=25">miter gates</a>. These are the large barriers that open and close at the ends of locks so that water can be added or removed to raise and lower ships. Changing water levels and repeated opening and closing of the gates stresses the structures and leads to development of fatigue cracks.</p>
<p>Draining locks to repair gates when they develop cracks is expensive and time-consuming. We are carrying out tests in which we make a small crack in the middle of a large steel plate, retrofit it with CFRP and then place it underwater and subject it to large stress cycles. Then we check the crack to see how effectively the fiber composites slow down crack growth rates. </p>
<p>So far we are finding that this is an effective way to slow the growth of underwater cracks, which could ultimately result in less frequent repair schedules and make repairs safer and more economical. The more innovative strategies like this that we can develop, the sooner we can raise our national infrastructure grades to levels that meets the nation’s expectations and that Americans can be proud of.</p><img src="https://counter.theconversation.com/content/69748/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hussam N. Mahmoud is chair of the American Society of Civil Engineers' Steel Bridges Committee and Fatigue and Fracture Committee.</span></em></p>Old and degraded infrastructure costs the United States money and puts lives at risk. A civil engineer describes some innovative ways to measure risks and prioritize repairs.Hussam N. Mahmoud, Assistant Professor of Civil and Environmental Engineering and Director, Structural Laboratory, Colorado State UniversityLicensed as Creative Commons – attribution, no derivatives.