How can structural engineers contribute to disaster mitigation?

Disasters have long impacted our world – from earthquakes and flooding, to more modern troubles of cyber-attacks and oil spills, human populations are at risk to a wide range of disasters posed by the ever changing natural and man-made environments in which they live.

Da Silva (2012) clearly highlights the ever increasing risk that the world is facing. Around two-thirds of the world’s population live in urban centres and as these sprawl, a larger number of people may be affected by a single disaster. As the effects of disasters escalate, the demand for post-disaster aid will increase. The Guardian disaster network (2013) estimated that for every $100 spent on disaster relief, less than $1 is spent on disaster preparedness and prevention. Twigg (2001) reported that for every $1 spent on disaster preparedness, between $2 and $7 is saved in disaster response. This disparity has encouraged disaster risk reduction initiatives that focus on preventing a disaster rather than picking up the pieces afterwards.

This post will explore the relationships between structural engineering and disasters, before discussing some of the ways in which our profession may be able to help mitigate the effects of such events.

Structural engineering and disasters

“By our actions we either compound disasters or diminish them”

Ban Ki Moon – 2011 Global Platform for Disaster Risk Reduction

When asked what a structural engineer does, I often answer that architects draw pictures of buildings and structural engineers make them stand up. However, here amongst colleagues, I propose that we are professionals who use materials to support loads.

Disasters can be defined as extreme events that result in great and often irremediable loss and ruin; however, such events could be described using an engineering rhetoric as those that impose extreme loads – be these perhaps physical, economic, environmental or societal.

Disasters are diverse, from those occurring naturally; volcanic eruptions; earthquakes; tsunamis; extreme cold, heat, wind, rain; and landslides, to man-made disasters such as nuclear leakages, oil spills, structural collapse, fire, terrorism and war.

It is striking that in many disasters engineering is culpable – indeed, we cause disasters! If engineering were ‘perfect’ there would be no nuclear leakages or oil spills, the Twin Towers might not have fallen (see Figure 1), Fukushima Daiichi would have shut down as designed and Ronan Point might still be standing (see Figure 2). Furthermore, there are examples where an engineering solution has mitigated one type of disaster, but worsened the effects of another. This is typified by concrete roofs, now rubble, on Haitian streets; heavy enough to stay put during a hurricane, yet heavy enough to kill inhabitants during an earthquake.

Figure 1 - Collapse of the South twin tower, New York. © Associated Press/Jim Collins

Moreover, when buildings collapse and kill in a developing world earthquake, have we failed by not sharing and impressing our expertise in materials, design methods, quality assurance procedures and construction techniques with those more vulnerable? Are we therefore partially to blame? Do we thus have a moral responsibility to endeavour to ease Haitian type suffering?

Thus, on reflection, perhaps a new category of ‘engineering-made disasters’ should be coined, which occur as a result of imperfect engineering. Indeed, it might be broken down further into ‘structural engineering-made disasters’.

Achieving ‘perfect’ engineering globally would effectively remove engineering-made disasters. Despite perfection being a fanciful ideal, we must nevertheless strive to be the best engineers that we can possibly be; we must as a profession learn from experience; we must ensure that we write, conform to and enforce correct and up-to-date codes and standards and we must rigorously check each other’s work.

The responsibility on our shoulders is great; we must carry as best we can. 

Figure 2 - Ronan Point after the partial collapse © Daily Telegraph

Mitigation using technical structural engineering skills

Structural engineers, with our specific set of technical skills, are uniquely positioned to abate disasters. To illustrate how these could apply to disaster mitigation, let us imagine that a small fictitious island exists with one main settlement. A number of structural engineers live and practise amongst the population. It comes to the attention of the government that a disastrous event is approaching, somehow they know for certain what will occur and when. The islanders come together to discuss what can be done to mitigate the impact of the impending disaster. What will the structural engineers do? Clearly, the answers depend on the type of disaster and the time, money and materials available, thus let us assume there are plentiful resources at hand.

If the disaster were an earthquake, the structural engineers would set about assessing the vulnerability of structures and designing retrofitting to strengthen where necessary. Collapse-related deaths are reduced, post-earthquake schools can run, banks can trade, hospitals can operate – the disaster is mitigated. If the disaster were a tsunami, the structural engineers would set about designing and building tsunami defences high enough and strong enough to deal with the threat. Again, the disaster is mitigated. If the disaster were a hurricane, buildings could be retrofitted to deal with the associated loads.

But, what would the structural engineers do in the shadow of an impending volcanic eruption? They could ensure that buildings were capable of dealing with increased roof loads caused by ash. However, what if pyroclastic flows were destined to head straight towards the settlement, potentially destroying everything in their way, as in Figure 3? Thus far, mitigating this volcanic hazard through structural engineering has been considered implausible. But is it? If we really had to make something work with limitless resources, could we design a structure to divert such a flow? What are the dynamic loads? What are the temperatures? What size flow needs to be diverted?

Such concepts may be a little ‘blue sky’ for some, but should we not be imaginative in our thinking about these problems? I wonder, can we build cities on base isolating springs? Can we construct Richard Buckminster Fuller’s geodesic dome to protect cities from extreme weather? Can we divert pyroclastic flows and lahars away from settlements? I reason that our first question should always be, ‘can it be done?’ followed later by ‘is it practicable?’ since if we fail to stretch our engineering minds, progress may not be realised. However, it is important to retain the ability to recognise the limitations of engineering, particularly when a more workable solution should be favoured.

To summarise, structural engineers have technical skills and knowledge to help to protect structures from disasters. Through this, our involvement will help to save lives, protect assets, reduce the need for disaster relief aid and ensure resilience.

Despite structural engineers having a lot to offer, I would hasten to add that we do not have all of the answers. Our contributions to disaster mitigation must complement the work of a motivated and sufficiently resourced team, who as a whole, deliver comprehensive and therefore effective solutions.

Mitigation by applying structural engineering processes

Disasters rarely occur alone and are often compounded by subsequent misfortunes as a result of the first. If a mitigation solution does not contain adequate robustness, there remains the possibility that a single disaster event will trigger a cascade of supervening difficulties. For example: an earthquake causes a tsunami, which causes flooding resulting in a disease epidemic and a power supply failure to the hospital rendering it unable to treat the ill and injured. This potential succession of incidents must all be considered when attempting to prevent or prepare for disasters.

Figure 3 - Pyroclastic flows from the Soufriere Hills Volcano engulfing abandoned settlements, Montserrat.

© Dr Paul Cole.

Structural engineers design structural systems for disproportionate collapse to ensure that buildings do not collapse except in a proportionate event. This designed robustness ensures that in the event of failure of part of the structural system, the whole structure does not fail. The same principles could – and should – be applied to disaster scenarios; planning and designing a robust system that stands during a disaster, from beginning to end.

When designing a structural system, engineers satisfy the ultimate limit state by ensuring that each element (and therefore the whole system) can support the maximum design loading. The serviceability limit state is also satisfied by ensuring that each element (and therefore the system as a whole) remains fit for use. Again, these rules should also be applied to disaster mitigation systems. The system should be designed with adequate capacity to prevent failure, ensuring that lives are preserved; hospitals operate; and governments continue governing. Assuming that the ultimate limit state has been satisfied, the serviceability limit state should ensure that, soon after the disaster event, the population are able to complete day-to-day activities such as going to work, attending school, washing clothes, etc.

To synopsise, a complete disaster mitigation plan needs both capacity and robustness, processes that structural engineers practise each day; hence, we are able to view the disaster prevention in new and fresh ways to ensure that the correct requirements are satisfied using the right processes.

To conclude, I will reiterate my beliefs that structural engineers can help to mitigate any disasters, simply by applying and adapting both what we know technically and the processes that we use in our everyday work.

Charities, governments and aid agencies must begin to release funds for application to disaster preparedness and prevention, instead of waiting until the disasters have already occurred. This has started to happen but often without structural engineers at the table. This needs to change. We need to impress the powers that be that we are needed at that table, at every stage and every level, perhaps by reminding them of the simple fact that many disasters could be mitigated through ‘perfect’ engineering.

References

Da Silva, J (2012), Shifting Agendas: Response to Resilience – The role of the engineer in disaster risk reduction, ICE Brunel Lecture

Guardian development network, 2013. Insurance only part of disaster resilience, says climate change panel. The Guardian Online, [online] (Last updated  16.14 GMT 06^th March 2013) Available at: < http://www.guardian.co.

uk/global-development/2013/mar/06/insurance-disaster-resilience-climate-change> [Accessed 08^th April 2013].

Twigg, J., 2001. Physician, Heal Thyself?  The Politics of Disaster Mitigation.  London: Benfield Greg Hazard Research Centre, University College London.