Resilience-based earthquake design of tall buildings

Growth of the world’s urban population is increasing demand for working and living space in cities. To control traditional urban sprawl and transport inefficiency the current trend is to create more compact, denser cities. This has triggered a resurgence in tall buildings for residential, commercial and mixed uses.

Much of this new construction upward is located in highly seismic urban zones. While earthquakes pose a significant threat to communities, current state-of-the-art design guidance is based on performance objectives from building codes which permit significant damage as long as life safety is achieved. The code does not focus on earthquake resilience, the ability of an organisation or facility to regain functionality quickly after an earthquake.

Our project aimed to determine cost-effective design strategies that will lead to more earthquake-resilient tall buildings, minimising financial losses and functional recovery time.  The project team designed and analysed a prototype of a modern tall residential building to quantify the current baseline values for these losses. The team then identified the key factors contributing to losses and evaluated enhancements for improving the design and performance to address these factors.

For modern tall buildings in highly seismic zones, the estimated downtime following a significant earthquake is approximately two years.

The most effective way to avoid this downtime would be to design the building, including non-structural components, so it remains relatively undamaged in a seismic event.

This study shows that the performance of the building substantially improved following application of the resilience-based design approach in the REDi™ rating system (developed by Arup). This resulted in significantly less downtime after a seismic event, and this can be achieved for a fraction (less than 2%) of the initial building cost.

This study illustrates the economic benefits of resilience-based design and proposes design solutions for improving performance. These design solutions span a wide range of categories, including enhancements to structural systems, architectural components, egress systems, and mechanical and electrical components.

Arup has successfully applied the concepts developed in this project to the design of the 181 Fremont Tower in San Francisco. The outcomes of this project are relevant to developers, architects and engineers who are creating new high-rise buildings in highly seismic urban zones. The result was tall building that is arguably the most resilient on the west coast of the US. This has differentiated the building in the marketplace and helped the developer in marketing it to tenants.

As urban developers continue to plan and build tall buildings in the high-seismicity regions, seismic design is become more and more important. Existing codes are not sufficient. Arup’s work in this area demonstrates new, cost-effective technologies for constructing higher performing, more resilient buildings that have already be successfully applied in tower construction projects in the US.