Investigating the impact of design criteria on the expected seismic losses of multi-storey office buildings

Abstract

The Ministry of Building, Innovation and Employment is developing advice on how to deliver Low Damage Seismic Design (LDSD) protection for buildings through their Tū Kahika: Building Resilience platform. The draft LDSD advice is considering a design drift limit for multi-storey buildings of 0.5% as part of new damage control limit state design checks. The potential impact of this design criterion on the expected annual loss due to repair costs is investigated for generic reinforced concrete wall case-study office buildings of 4- and 12-storeys in both Wellington and Christchurch. The equivalent static method, in line with NZS 1170.5 and NZS 3101, was used to design the buildings to conventional and draft LDSD specifications, representing current and future state-of-practice designs. The draft LDSD advice aims to limit the expected annual loss of complying buildings to below 0.1% of building replacement cost. This research tested this expectation. Losses were estimated in accordance with FEMA P-58, using building responses from non-linear time history analyses. Although it is found that the new drift limit alone may not limit seismic losses to the target values owing to damage to acceleration-sensitive elements, the results do support the intentions of the draft design advice to significantly reduce the expected seismic losses of complying buildings. The study also highlighted the importance of using an accurate approximation of RC wall stiffness for LDSD, and provides insight into different design strategies that could be followed to effectively limit losses in RC wall buildings as part of LDSD.