The response of tall buildings to far-field earthquakes and the case of a 49-storey steel building

This paper investigates the seismic response of an instrumented 49-storey steel structure in San Francisco to weak, far-field, and strong, near-field ground motions. The instrumentation records obtained during the 1989 Loma Prieta earthquake are used to verify the accuracy of the predictions of the time-history analysis of the model. The ChiChi-002 ground motion record from the 1992 Chi-Chi earthquake in Taiwan (PGA = 0.08 g), representing a 'weak, far-field' earthquake and the record from the 1994 Northridge-Newhall earthquake (PGA = 0.60 g) representing a 'strong, near-field' earthquake were used in the study. The results showed that the force, acceleration, and displacement responses of this long-period structure to the 'weak far-field' ground motion are much larger than its response to the 'strong, near-field' ground motion. Also, the response attenuates at a slower rate for the weak, far-field earthquake, indicating the possibility of greater damage, both to structural and non-structural elements, during the earthquake. Interim seismic design recommendations are formulated to address this issue in the design of tall buildings with long periods.