Too often in earthquake engineering, sustainability considerations are sidelined in an effort to save time and money. The industry needs to realise that incorporating sustainability into routine seismic design makes economic, social and environmental sense.
Sustainability means meeting the demands of today without compromising the needs of future generations. In the context of engineering, this can mean a range of things, from using recyclable materials which cause less waste and pollution, to constructing buildings which are able to recover from natural disasters.
The major principle of earthquake design is to introduce resilience in buildings – typically, we achieve this by designing the foundations in such a way that, during seismic incidents, the superstructure is affected before the substructure, avoiding foundational damage.
Resilience is a sustainable concept, but that doesn’t mean seismic design is automatically sustainable. As engineers, we play a crucial leadership and influencing role in making seismic design sustainable through astute assessment of seismic risk, and careful judgment of the best way to mitigate it.
There will always be conflicts when trying to match differing demands of stakeholders, the environment and economics in delivering earthquake resilience. Our challenge is to balance these demands in the most sustainable way.
Economic, social and environmental impacts
The financial impact of building loss following a seismic event can be enormous. For example, the Great East earthquake in Japan in 2011 caused US$211,753 million in direct losses. Rehabilitation and reconstruction create cost, and our Infrastructure Carbon Review shows that avoiding unnecessary construction is key in order to reduce the carbon emissions associated with infrastructure.
Moreover, disruption caused by earthquake damage to infrastructure can have a major ‘cascade failure’ effect on businesses and people. By improving the seismic performance of infrastructure, we avoid or reduce earthquake damage, and we significantly reduce seismic incidents’ impacts on the environment, economy and community.
Engineers must consider the sustainability impacts of any seismic intervention. Here are three key issues to address:
- 1. Retrofit to avoid rebuild. Seismic design must extend beyond new-build projects. We need to ensure existing buildings are retrofitted so that they perform better in future earthquakes. The business case is clear: a building can be retrofitted for seismic resilience at around 5% of the cost of its reconstruction following an earthquake collapse. Governments and the World Bank are undertaking major seismic retrofitting schemes worldwide, and Mott MacDonald is providing technical support on a number of these in different parts of the world.
- 2. Unnecessary strain on resources. Seismic design often involves dealing with uncertainties and applying a suitable factor of safety to design for the most unlikely conditions. Choosing a factor of safety that is too high could put unnecessary strain on resources, which in turn affects future generations. We must keep studying seismic incidents to ensure that engineers do not use extraordinarily high factors of safety purely because of ignorance. Dynamic soil structure interaction behaviour during earthquakes is one area that would benefit from more research.
- 3. Development and resilience in harmony. It is worth remembering that in many developing countries there is a perception that the demand for infrastructure overrides many other factors, including seismic resilience. We must be careful to ensure that seismic resilience interventions don’t compromise countries’ needs for infrastructure development.
Engineers need to minimise the carbon footprint of their buildings and think about climate change issues, all while delivering safe infrastructure. This is where seismic specialists can provide value in a challenging international work environment.