Stochastic analysis of the risk of seismic pounding between adjacent buildings

Seismic pounding can induce severe damage and losses in buildings. The corresponding risk is particularly relevant in densely inhabited metropolitan areas, due to the inadequate clearance between buildings. In order to mitigate the seismic pounding risk, building codes provide simplified procedures for determining the minimum separation distance between adjacent buildings. The level of safety corresponding to the use of these procedures is not known a priori and needs to be investigated. 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 behaviour. The seismic input is modelled 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 specific statistics of the response processes. The proposed procedure is applied to estimate the probability of pounding between linear single-degree-of-freedom systems and to evaluate 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 probability of pounding between adjacent buildings modelled as multi-degree-of-freedom systems.