Characteristics of Earthquake Performances of Bridge under Multi-support Excitation with Consideration of Site Effects
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摘要: 本研究拟从常规桥梁（跨径不超过150m且桥长不超过600m）出发，考虑局部场地效应，对某工程场地的地震反应进行三维动力有限元分析。将计算得到的地表地震动作为桥梁桥墩处的非一致输入，然后再通过有限元时程分析计算得到桥梁的地震反应。通过与一致激励及考虑行波效应激励的地震反应计算结果进行比较，得出以下结果：由于局部场地条件对地震动的频谱、峰值加速度都有影响，与一致激励相比，考虑局部场地的非一致激励对于桥梁的下部结构反应影响较小，而对于上部结构响应影响明显；考虑行波效应的非一致激励对于桥梁地震响应有减弱效果。研究结果表明，仅考虑行波效应引起的地震动非一致性开展桥梁地震响应分析并不具备保守性。Abstract: In this study, we intend to start from the conventional bridge (span is less than 150m and length is less than 600m), calculating the earthquake response of an engineering field through three-dimensional dynamic finite element simulation for multi-support excitation with consideration of local site effect. Then the seismic response of the bridge is calculated through the finite element time history analysis. By comparing the traveling wave effect and uniform excitation we obtained the following results:Because of the Fourier spectrum and peak acceleration of the input wave have been changed due to the site effect, compared with the uniform excitation, multi-support excitation consider local site effect has little effect on lower part of the bridge structure, but for the upper structure of the bridge is relatively large; multi-support excitation consider traveling wave effect on the seismic response of the bridge is decreased obviously. We conclude out that multi-support excitation consider traveling wave effect only is not conservative.
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Key words:
- Site effect /
- Multi-support excitation /
- Traveling wave effect /
- Bridge
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图 2 土层分布及桥墩位置（单位：m）
Figure 2. Distribution of soil layer and position of bridge piers(unit: m)
图 3 输入地震动时程A0（蓝色）与输出地震动时程A1至A14（黑色）时程特性比较
Figure 3. Comparison of time histories between input wave (blue) and output wave (black)
图 4 1至4号工况下桥梁关键部位地震响应
Figure 4. Response of key position of the bridge under working conditions No.1 to 4
图 5 1、5、6号工况下桥梁关键部位的地震响应
Figure 5. Response of key position of the bridge under working conditions No.1, 5 and 6
表 1 桥梁模型振型
Table 1. Mode shape of the bridge model
阶次 频率/Hz 周期/s 1 0.4304 2.324 2 0.6081 1.644 3 0.6838 1.462 4 0.7826 1.278 6 0.9081 1.110 12 1.3642 0.733 20 2.3865 0.419 
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表 2 土层物理及力学参数
Table 2. Physical and mechanical parameters of soil
土层类别 成分 剪切波速/m·s－1 密度/kg·m－3 泊松比 瑞利阻尼系数β 淡黄色 表面黏土 234 1.49 0.40 0.20 绿色 淤泥质土 211 1.40 0.44 0.15 青色 淤泥质黏土 288 1.46 0.40 0.15 黄色 粘土 355 1.57 0.40 0.14 蓝色 黏土夹角砾 487 1.59 0.40 0.11 红色 白云质灰岩 780 1.93 0.34 0.10
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表 3 全部工况下桥梁关键部位地震响应的最大值
Table 3. The maximum response of key position of the bridge under all working conditions
工况 墩顶位移/m 基底应力/MPa 主梁应力/MPa 胯间支撑应力/MPa 1 0.22 28.71 7.66 28.58 2 0.25 30.42 9.64 32.12 3 0.26 33.28 8.29 30.18 4 0.24 29.35 8.30 28.79 5 0.20 22.99 4.62 25.73 6 0.22 28.40 7.57 28.74
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