Analysis of the seismic response characteristics of building structures subjected to near-fault ground motions from Wenchuan earthquake

This paper focuses on studying the effects of near-fault ground velocity pulses on building structures. Inter-story drift distributions of structures subjected to velocity pulse-type records and non-pulse-type records were investigated to reveal the effects of near-fault strong motions on building structures with different natural vibration periods. Two groups of typical velocity pulse records and non-pulse records were selected from Wenchuan M_S8.0 earthquake, and a wavelet method of time domain synthesizing was used to modify the selected records, matching the target spectra from determined seismic intensity. The modified ground motions were used as the basic strong motion data for seismic response analysis. Finite models of 3, 11 and 20-story RC frame structures were established, and inter-story drift distributions of these three buildings subjected to typical velocity pulse-type records and non-pulse-type records were investigated. The study reveals that the inter-story drift distributions are quite different when the structures are subjected to pulse-type records and non-pulse-type records for the 3, 11 and 20-story RC frame structures, and are correlated with the natural vibration properties of building structures. In terms of low-rise buildings, inter-story drifts are larger for non-pulse-type records than those for pulse-type records. The influences of high modes on inter-story drifts become much more obvious with the increase of story number. The median value and dispersion of inter-story drifts are much larger when subjected to pulse-type records compared with non-pulse-type records for high-rise buildings. Pulse-type records tend to induce higher modes response, resulting in large inter-story drifts for high-rise buildings. Non-pulse-type records have relatively large effects on inter-story drifts primarily in the fundamental mode for low-rise buildings. It can be concluded that the effects of near-fault velocity pulses should be taken into consideration when assessing seismic damage potential for near-fault building structures.