Quantiles of critical separation distance for nonstationary seismic excitations

An assessment of quantiles of the separation distance to avoid the pounding of two adjacent buildings under seismic excitations is presented. The seismic excitations are modeled as a nonstationary random process, and the problem is formulated based on structural reliability methods and the random vibration theorem. The formulation includes the uncertainty in structural properties such as the natural vibration periods and damping ratios. Numerical analysis is carried out for assessing the quantiles of the critical separation distance between two adjacent buildings. These quantiles are compared with those obtained by using the complete quadratic combination (CQC) rule together with the quantiles of the structural peak responses that are calculated based on the two-sided crossing rate. The results obtained show that use of the CQC rule in this manner may significantly overestimate or underestimate the critical separation distance, depending on the damping ratios and the natural vibration periods of adjacent buildings. The trends of overestimation or underestimation on considering nonstationary excitations are similar to those obtained on considering stationary seismic excitations. However, the dispersion of the overestimation or underestimation for the former differs from that for the latter. (c) 2005 Elsevier Ltd. All rights reserved.