RESIDUAL FATALITY RISK ESTIMATES FOR SETTING EARTHQUAKE SAFETY REQUIREMENT

Structures designed strictly in accordance with the required code of practice could still have a small probability of collapse in a major earthquake. This is the residual risk, which should be lower than the level that is acceptable or tolerable by the public and stakeholders. The 2012 edition of the International Building Code (IBC) has firstly set out risk-targeted performance requirements for seismic design. However, the implications of the requirements for life safety have not been explicitly considered. This study addresses this gap by evaluating whether the stipulated requirements are adequate for mortality control or not. The annual individual fatality risk in different categories of buildings is first estimated and benchmarked against the tolerable level of mortality risk. A rational collapse risk limit is then proposed for structural design of different types of buildings. The paper also looks at some of the uncertainties associated with fatality estimation and the use of annualized mortality risk for design purposes.