Lumped mass models for use in predicting collapse of an isolated building

Development of fragility functions is an important step in the seismic evaluation of isolated buildings. To develop collapse fragility curves, a series of detailed dynamic ground motion analysis with multiple intensity measure levels must be conducted, often requiring considerable computational time. In addition, including more modeling detail to enable the prediction of multiple failure modes can make numerical convergence more challenging. Therefore, the possibility of simplified models to predict the collapse probability of isolated buildings is attractive. The collapse fragility curves derived from two lumped mass models with differing degrees of simplification are compared to a full nonlinear model. This is done for both sliding and rubber bearings with varying moat wall or restraining rim (for sliding bearings). The comparison demonstrates that the simplified model proposed in this study can be a potential alternative for estimating fragility functions of isolated buildings, as they can significantly improve the computational efficiency with relatively small compromises on accuracy. This will allow for faster validation of system design when incorporating performance targets under large earthquakes.