Reliability-based assessment of seismic pounding risk between adjacent buildings

Earthquake ground motion excitation can induce pounding in adjacent buildings with inadequate separation distance. This hazard is particularly relevant in densely inhabited metropolitan areas, due to the very limited space among buildings. Existing procedures for minimum separation distance are based on approximations of the peak relative horizontal displacement between adjacent buildings, and are characterized by unknown safety levels. The present study proposes a reliability-based procedure for assessing the level of safety corresponding to a given value of the separation distance between adjacent buildings exhibiting linear elastic behavior. The seismic input is modeled as a nonstationary random process, and the first-passage reliability problem corresponding to the pounding event is solved employing analytical techniques involving the determination of some specific statistics of the response processes. Comparison of computed analytical results with numerical simulation results are also shown, in order to validate the proposed methodology. The proposed procedure is employed for evaluating the reliability of simplified design code formulae used to determine building separation distances. Furthermore, the capability of the proposed method to deal with complex systems is demonstrated by assessing the effectiveness of the use of viscous dampers, according to different retrofit schemes, in reducing the pounding probability of adjacent buildings modeled as multi-degree-of-freedom systems.