Effect of aftershock intensity on seismic collapse fragilities

This paper presents a procedure to compute the sensitivity of a mainshock (MS)‐damaged building's collapse probability to earthquake intensity as a function of magnitude or site‐to‐source distance. Specifically, the effect of earthquake magnitude and spatial distribution of aftershocks on collapse fragilities is investigated. Aftershock (AS) fragilities for different site‐to‐source distances are examined by performing incremental dynamic analysis (IDA) using a sequence of MS+AS ground motions. The effect of MS damage is to alter the fragilities which can be quantified for the building investigated. It is observed that the collapse fragilities have a reasonable variation in collapse probabilities with changing AS magnitude and/or site‐to‐source distance.