地震动作用下刚体扭转效应的振动台模拟试验

2008年汶川地震中江油市太白公园曲径桥上的石雕发生转动破坏现象，本文对这一转动现象进行了振动台模拟试验。模拟试验结果表明:① 在振动台三向加载1.5倍的汶川地震江油台记录的平动加速度后，模型的转动情况与实际观测的石雕转动情况比较一致；② 石雕的转动与石雕的非对称性、地震动输入角度和地震动的竖向作用有关；③ 加载竖向地震动作用后，石雕模型会发生摇摆现象，说明竖向地震动是造成模型扭转现象的重要原因，这也说明在分析相似震害现象时竖向地震动作用不可忽视。 

A shake table test for the rotation response of rigid bodies under seismic excitation

In 2008 Wenchuan earthquake, an interesting torsion phenomenon attracts our attention: Most of the stone statues, which were placed upon the banisters of one zigzag bridge in Taibai Park, Jiangyou City, Sichuan Province, rotated an angle from their original location with little translation displacements. To simulate and further study this phenomenon, a group of stone statue models with different asymmetric characteristics were made, and then they were arranged in different location and direction on the shake table to do shake tests. The results show that: ① The torsional phenomena of the statue models appeared when input 3D accelerations from the shake table, and the acceleration amplitudes are 1.5 times of the original seismic records. Also, the phenomena were similar to those in the Taibai Park in Wenchuan earthquake. However, when the input accelerations were only in two horizontal directions, the torsional phenomena would not appear even when the amplitude was large enough. ② The torsional phenomena of the stone statue models showed different modes with different model asymmetric characteristics and different acceleration input angles. ③ The most significant factor that causes the torsional phenomena is the vertical seismic input. The statue rotation did not occur without it. So for this case, vertical ground motion is crucial and cannot be ignored.