地下商场结构对地面运动影响的振动台试验研究

Shaking table test of the effect of underground shopping mall structure on ground motion

为了研究地下空间结构对场地地震反应的影响,以一个三层地下商场结构为原型,设计并开展了土-地下空间结构动力相互作用振动台模型试验,研究了在6条不同卓越频率输入地震波在不同峰值加速度下场地地震反应的变化规律。试验研究结果表明:(1)地表水平加速度放大系数以结构中轴线为对称轴呈对称分布,地下结构显著影响上方及邻近场地的地表水平加速度。同时,由于地下空间结构的局部场地效应影响,即使在水平地震输入下也将导致场地产生竖向振动,地表竖直加速度放大系数呈M形分布。地下空间结构的影响范围可达到其两侧各一倍宽度距离。(2)地表加速度放大系数受输入地震波卓越频率的影响明显,且随着输入地震波的峰值加速度(PGA)的增大而降低,但空间放大系数随着PGA的增大而增大。(3)地表加速度Fourier谱的峰值频率受输入地震波的卓越频率、场地水平方向的固有频率和竖向固有频率的综合影响。

To study the influence of underground space structure on ground motion,a shaking table test of soil-underground structure dynamic interaction was designed and carried out with a three-story underground shopping mall structure as a prototype.Six seismic waves with different predominant frequencies and peak accelerations were regarded as input waves to test ground motion.The experimental results show that the amplification factor of horizontal acceleration of ground surface is symmetrically distributed along the axis of the underground structure.The underground structure significantly affects the horizontal acceleration of the ground surface above and adjacent to the sites.At the same time,due to the local site effect of underground space structure,vertical vibration will occur even under horizontal seismic excitations.The amplification factor of vertical acceleration of ground surface is distributed as M-shaped.The influence range of underground space structure can reach a distance equal to its own width on both sides.The amplification factor of acceleration of ground surface is obviously affected by the predominant frequency of input seismic wave,and decreases with the increase of peak ground acceleration(PGA),but the space amplification factor increases with the increase of PGA.The peak frequency of ground acceleration Fourier spectrum is influenced by the predominant frequency of seismic waves,natural frequencies in horizontal and vertical directions of soil site.