Effects of rupture directivity and fling step of near-fault ground motions on seismic responses of long-period structures

摘要

Near-fault ground motion recordings from two different earthquake events, i. e. Chi-Chi, Taiwan earthquake (Sep, 21, 1999) and Northridge earthquake (Jan, 17, 1994), are selected as seismic input, and the influence of characteristics of near-fault ground motions including rupture forward directivity and fling step on the seismic responses of single degree of freedom (SDOF) system, base-isolated building and cable-stayed bridge is analyzed systematically. The computational results illustrate that the effect of rupture directivity and fling step of ground motions on the seismic responses of engineering structure is period-dependent. In the interval of short and medium period, the spectral acceleration of ground motions with fling step effect is possibly greater than that with forward directivity. And in the long period region, the spectral acceleration of ground motions with forward directivity effect is generally greater than that with fling step. Moreover, the near-fault pulse-like ground motions force larger dynamic responses to long-period structures, and increase the seismic design demands of these structures remarkably.