Large coseismic displacements and tall buildings

摘要

Seismic demands imposed on tall buildings are sensitive to long-period ground motions. A source of thesenmotions can be near-fault effects: rupture directivity and fling step (large coseismic displacements). Thenpotential adverse effects of near-fault motions on structures have been attributed to rupture directivity innprevious studies. However, the influence of large coseismic displacement on tall building seismic responsenhas not been widely investigated. This study explores the influence of coseismic displacements on the nonlinearnresponse of tall buildings. Several nonlinear time history analyses were performed to evaluate the responsenof a reinforced concrete tall building to coseismic displacements. The ground motions used for thesenanalyses were recorded in the proximity of faults where large coseismic displacements have been observed.nRecorded motions from the Landers earthquake (1992), Kocaeli earthquake (1999), Tohoku earthquaken(2011) and Chi-Chi earthquake (1999) were selected for this study. The results from a parametric studynof the response of a single-degree-of-freedom system showed that the influence of the fling on the systemnresponse is dependent on (a) the ratio of fling rise time to the fundamental period of the system and (b)nthe yielding resistance of the structure. At the onset of yielding, the fling step can further drive the systemninto very large displacements. The results from the case study indicate a significant increase on the seismicnresponse of a tall building when the fling effect is included in the ground motions. This issue is a concernnfor tall buildings in regions where faults are not mapped to a great extent and near-fault fling effect could benproduced by a large magnitude earthquake. Copyright © 2011 John Wiley & Sons, Ltd.