Mitigating seismic risk through performance based design

At Arup, we’re creating safer and more resilient communities in Turkey by using performance-based design to create earthquake-resistant and cost-effective structures.

Turkey is one of the most earthquake-prone countries in the world. The North Anatolian Fault (NAF) stretches across the country and has been responsible for many of Turkey’s major earthquakes.

Working in these conditions, we have accumulated unrivalled experience and skills in seismic design as well as in specialist fields such as seismology, geotechnical and structural engineering, risk assessment and management. This enables us to comply not only with Turkey’s seismic design specifications but also with international seismic codes and standards.

Performance-based design, assessment and retrofit

But we don’t simply follow codes to the letter when we can achieve better performance through innovative engineering. Performance-based seismic design evaluates how a structure building is likely to perform under determined potential hazard, considering uncertainties inherent in the quantification of potential hazard and uncertainties in assessment of the actual building response. Moreover, it permits owners and other stakeholders to quantify financially or otherwise the expected risk to their buildings and to select a level of performance that meets their needs while maintaining a basic level of safety.

The cost of seismic retrofit, if done to comply with the prescriptive code requirements developed for design of new buildings, may be too high for economic feasibility and may not provide the performance intended.

In contrast to conventional design approaches, performance-based design provides a systematic methodology for evaluating the performance capability of a structure. It can be used to verify the equivalent performance of alternatives, achieve standard performance at a reduced cost, or confirm higher performance needed for critical facilities. Additionally, long-term retrofit cost reducing innovative approaches to solve the problems of seismic engineering are based on the addition of special instruments to their conventional structural systems, with the aim of enhancing the control of their seismic performance.

Crucially, we obtain site-specific seismicity data for every major seismic design project. For example, we identified the fault line adjacent to the Toyota Factory site in Gebze from space imagery. By taking this into consideration in our design, we ensured the factory suffered no damage in the major 1999 Kocaeli and Düzce earthquakes.

Performance targets

Through our approach we make sure that performance targets are met at different levels of ground shaking. We’ve put this into practice in major projects like the Ford Factory in Gölcük. Following seismic assessment studies, we were invited by the client to continue the works to carry out retrofit design of the plant structures. We were also responsible for the infrastructure design of the plant site, the compound area and the jetty.

Another example is Sabiha Gökçen International Airport (SGIA), in which our design for a new terminal uses 300 isolators to reduce lateral earthquake loads by 80%, enabling it to withstand an earthquake of 7.5-8.0 on the Richter scale. The building, at over 40,000m2 on plan, is the largest seismically isolated structure built to date.

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    • Toyota Factory, bird's view. ©Arup

      The fault line adjacent to site boundaries of the Toyota Factory was identified by Arup.