A shake table test for the rotation response of rigid bodies under seismic excitation
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摘要: 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。Abstract: 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.
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Keywords:
- Wenchuan earthquake /
- rotation effect /
- shake table /
- simulation test /
- vertical seismic excitation
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图 7 试验后各模型的位移及旋转角度示意图
Figure 7. Displacements and rotational angles of each model after test
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图 1 江油市太白公园曲径桥和桥上石雕在汶川地震中的转动破坏现象（Yang et al，2010）
Figure 1. Rotation damage phenomena of stone carvings on the labyrinth bridge in Taibai Park of Jiangyou City in Wenchuan earthquake （Yang et al，2010）
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图 4 模型在振动台上的布置和编号（a）及测量仪器的位置（b）
Figure 4. Layout and number of models on the shake table （a） and the location of measuring instrument （b）
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图 5 江油地震台东西方向（a）、南北方向（b）和竖向方向（c）的加速度记录
Figure 5. Acceleration time histories of EW （a），NS （b） and UD （c） directions for Jiangyou seismic station
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图 6 模型7在工况12下x方向的加速度（a）和位移（b）时程曲线
Figure 6. Acceleration （a） and displacement （b） time histories of model 7 in x direction under working condition 12
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图 8 试验后模型在振动台上的损伤状态
Figure 8. The damage state of models 4，6，7 and 8 on the shake table
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图 10 模型2在三向地震动加载作用下的运动片段
Figure 10. The move segments of model 2 under three-direction seismic excitation
表 1 振动台试验加载工况
Table 1 Loading working conditions of shake table test
工况序号 输入地震波 输入地震动峰值/g 工况序号 输入地震波 输入地震动峰值/g x方向 y方向 x方向 y方向 z方向 1 El-Centro波 0.03 0.03 7 El-Centro波 0.1 0.1 0.1 2 0.05 0.05 8 江油台地震波 0.027 0.031 0.011 3 江油台地震波 0.013 0.016 9 0.036 0.042 0.014 4 0.023 0.026 10 0.045 0.052 0.017 5 0.036 0.042 11 0.054 0.063 0.021 6 0.045 0.052 12 0.068 0.079 0.026 
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表 2 各个模型的位移和转角
Table 2 Displacement and rotational angle of each model
模型编号 x向位移/mm y向位移/mm 模型绕中心的转角/° 1 6 80 18 2 33 28 0 4 28 27 21 6 6 14 21 7 19 21 31 8 34 7 15
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