How do forensic engineers investigate bridge collapses, like the one in Miami?

The collapsed pedestrian bridge in Miami. Image: Getty.

On 15 March, a 950-ton partially assembled pedestrian bridge at Florida International University in Miami suddenly collapsed onto the busy highway below, killing six people and seriously injuring nine. Forensic engineers are taking centre stage in the ongoing investigation to find out what happened and why – and, crucially, to learn how to prevent similar tragedies in the future.

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 National Academy of Forensic Engineers. 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 survivors are rescued and victims are recovered. 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 large equipment to break up massive blocks of concrete so that victims’ bodies could be recovered.


In Miami at the moment, forensic engineers and technicians from the National Transportation Safety Board 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 sequence of events and locations of key problems. Of course, they’ll also talk to witnesses to find out what workers and passersby saw and heard around the time of its collapse.

Then they’ll combine and analyse 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.

Weakness in partial structure

The FIU bridge was being built using a method called “accelerated bridge construction,” with separate sections 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.

Two key elements of the bridge design, the tall centre pylon and pipe supports, 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 until next year, so it’s likely that the project’s designers and engineers expected the bridge segment to hold while construction continued.

An artist’s rendering of what the final bridge was supposed to look like. Image: City of Sweetwater.

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.

Searching for clues

There are some other publicly available clues, too, that shed light on avenues likely under investigation already. Dashcam video of the bridge collapse 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 crack had been discovered near the bridge’s north end.

Additionally, the bridge span might have been either undergoing stress testing or other adjustments 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.

There will be other questions too, like “Why didn’t they use temporary supports to shore up the bridge?” 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.

Some of those questions will not be entirely engineering-related. For example, many are asking “Why wasn’t the road closed?” The Tamiami Trail was shut down for a few hours while the bridge span was put in place. 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 public safety or traffic congestion.

The ConversationAt 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 leading centres for accelerated bridge construction is right on the FIU campus.

Martin Gordon, Professor of Manufacturing and Mechanical Engineering Technology, Rochester Institute of Technology.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Community-powered policies should be at the top of Westminster’s to do list

A generic election picture. Image: Getty.

Over the past five decades, political and economic power has become increasingly concentrated in the UK’s capital. Communities feel ignored or alienated by a politics that feels distant and unrepresentative of their daily experiences.

Since the EU referendum result it has become something of a cliché to talk about how to respond to the sense of powerlessness felt by too many people. The foundations of our economy have been shifted by Brexit, technology and deindustrialisation – and these have shone a light on a growing divergence in views and values across geographies and generations. They are both a symptom and cause of the breakdown of the ties that traditionally brought people together.

As the country goes through seismic changes in its outlook, politics and economy, it is clear that a new way of doing politics is needed. Empowering people to take control over the things that affect their daily lives cannot be done from the top down.

Last week, the Co-operative Party launched our policy platform for the General Election – the ideas and priorities we hope to see at the top of the next Parliament’s to do list. We have been the voice for co-operative values and principles in the places where decisions are made and laws are made. As co-operators, we believe that the principles that lie behind successful co‑operatives – democratic control by customers and workers, and a fair share of the wealth we create together – ought to extend to the wider economy and our society. As Labour’s sister party, we campaign for a government that puts these shared values into practice.

Our policy platform has community power at its heart, because the co-operative movement, founded on shop floors and factory production lines, knows that power should flow from the bottom up. Today, this principle holds strong – decisions are best made by the people impacted the most by them, and services work best when the service users have a voice. Our policy platform is clear: this means shifting power from Whitehall to local government, but it also means looking beyond the town hall. Co-operative approaches are about placing power directly in the hands of people and communities.


There are many great examples of Co-operative councillors and local communities taking the lead on this. Co-operative councils like Oldham and Plymouth have pioneered new working relationships with residents, underpinned by a genuine commitment to working with communities rather than merely doing things to them.

Building a fairer future is, by definition, a bottom-up endeavour. Oldham, Plymouth and examples like the Elephant Project in Greater Manchester, where people with experience of disadvantage are involved in decision-making, or buses in Witney run by Co-operative councillors and the local community – are the building blocks of creating a better politics and a fairer economy.

This thread runs through our work over the last few years on community wealth building too – keeping wealth circulating in local economies through growing the local co-operative sector. Worker-owned businesses thriving at the expense of global corporate giants and private outsourcers. Assets owned by communities – from pubs to post offices to rooftop solar panels.

And it runs through our work in Westminster too – with Co-operative MPs and peers calling for parents, not private business, to own and run nurseries; for the stewards of our countryside to be farmers rather than big landowners; and for workers to have a stake in their workplaces and a share of the profit.

Far from being ignored, as suggested in last week’s article on community power, our work has never been more relevant and our co-operative voice is louder than ever.

Anna Birley is policy offer at the Co-operative party.