近断层地震动破裂向前方向性与滑冲效应对隔震建筑结构抗震性能的影响

选择台湾集集地震和美国北岭地震的近断层地震动记录作为输入,考察了近断层地震动破裂向前方向性与滑冲效应引起的两种不同速度脉冲运动对单自由度体系和长周期橡胶支座隔震建筑结构抗震性能的影响.反应谱分析表明,破裂向前方向性与滑冲效应对工程结构地震响应的影响是随结构周期变化的.在中短周期段,含破裂向前方向性效应地震动的谱加速度值大于含滑冲效应地震动的谱加速度值;而在长周期段,含滑冲效应地震动的谱加速度大于含破裂向前方向性效应的谱加速度值.并且,与无脉冲地震动作用相比,含破裂向前方向性与滑冲效应脉冲的近断层地震动作用下隔震建筑的地震响应显著增大.滑冲效应引起的速度脉冲使隔震建筑底部的层间变形和楼层剪力明显增大,这意味着滑冲效应脉冲比向前方向性效应脉冲对长周期建筑结构的破坏更具危害性.

Effects of rupture forward directivity and fling step of near-fault ground motions on seismic performance of base-isolated building structure

Near-fault ground motion records from two different earthquakes,the 21 September 1999 Jiji (Chi-Chi), Taiwan,earthquake and 17 January 1994 Northridge earthquake,are selected as seismic input,and the influence of velocitypulse of near fault ground motions with rupture forward directivity and fling step on the seismic performance of single degree of freedom (SDOF) system and base isolated buildings with lead rubber bearings are examined. The response spectrum analysis illustrates that the effects of rupture forward directivity and fling step of ground motions on the seismic responses of engineering structure are perioddependent. In the range of short and medium period, the spectral acceleration of ground motions with forward directivity is larger than that with fling step. In the long period range, the spectral acceleration of motions with fling step is generally larger than that with forward directivity. Furthermore, compared with the non pulse ground motions, the dynamic responses of base-isolated buildings under the ground motions with rupture forward directivity and fling step pulses are increased significantly. Moreover, the velocity pulses from the effect of fling step remarkably amplify the interstory drift and shear force of base isolated building at lower stories. This implies that the fling-step pulse causes more severe damage to long-period buildings than the forward directivity pulse does.