Plastic collapse mechanism of seismic assessment for existing RC bridges with flexible foundation and bearing pads
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摘要: 将钢筋混凝土桥墩墩顶在单位水平力作用下的变位, 分解为桥墩的弹性弯曲变位、基础转动产生的变位及基础平动产生的变位之和, 从而建立了一种计入弹性基础效应和弹性支座效应的钢筋混凝土梁桥横桥向抗震评估的塑性倒塌分析模型, 给出了等效弹性地震荷载计算方法、钢筋混凝土梁桥塑性倒塌分析计算公式及独柱墩在地震力作用下的双线性刚度实用分析方法。算例表明, 计入弹性基础效应和弹性支座效应后, 钢筋混凝土梁桥的最终抗震能力与结构延性明显下降。Abstract: The deformations of reinforcement concrete bridge piers were divided into three parts, elastic deformation caused by a unit horizontal force at the top of the bridge piers, the rotation deformation and foundation translation deformation. A plastic collapse mechanism analysis mode of seismic assessment for existing reinforcement concrete bridges with flexible foundation and bearing pads was developed. Its analysis procedures and formulas with respect to the effect of elastic ground and elastic bearings were newly derived, and the practical analysis approaches of bilinear stiffness of bridge piers were given. An improved analysis method of seismic assessment for reinforcement concrete bridges was derived from equivalent elastic response acceleration at the limit state by considering the variety of the structural displacement ductility capacity caused by flexible foundation and bearing pads. An example shows that the structural displacement ductility capacity of reinforcement concrete bridges and seismic capacity are apparently reduced owing to considering flexible foundation and bearing pads.
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Key words:
- bridge engineering /
- flexible foundation /
- ductility /
- plastic collapse mechanism /
- seismic assessment
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图 1 弹性基础单柱式墩顶的附加位移
Figure 1. Addition displacements of flexible-foundation single-column pier head
图 2 单柱式墩在水平地震作用下的变位
Figure 2. Displacement of single-column bent at unit horizontal force
图 3 钢筋混凝土截面M-h关系
Figure 3. Bilinear approximation of column moment-curvature relationship
表 3 不计弹性基础与弹性支座影响的评估
Table 3. Seismic assessment of bridge in spite of flexible foundation and bearing pads
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表 4 计入弹性基础不计弹性支座影响的评估
Table 4. Seismic assessment of bridge with flexible foundation but in spite of bearing pads
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表 5 弹性基础与弹性支座联合影响的评估
Table 5. Seismic assessment of bridge with flexible foundation and bearing pads
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表 6 不计弹性基础与弹性支座影响评估
Table 6. Seismic assessment of bridge in spite of flexible foundation and bearing pads
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表 7 计入弹性基础不计弹性支座影响的评估
Table 7. Seismic assessment of bridge with flexible foundation but in spite of bearing pads
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表 8 计入弹性基础与弹性支座影响的评估
Table 8. Seismic assessment of bridge with flexible foundation and bearing pads
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