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-  2018 

桩土作用对隔震梁桥地震易损性及震后通行能力影响
Influence of Pile-Soil Interaction on the Seismic Fragility and Post-earthquake Traffic Capacity of an Isolated Bridge

DOI: 10.3969/j.issn.1000-0844.2018.04.721

Keywords: 桥梁地震易损性,震后通行能力,桩土作用,转角延性比,平均损伤水平值
seismic fragility of bridges
,post-earthquake traffic capacity,pile-soil interaction,ductility ratio of rotation angle,average damage level

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Abstract:

为确定桩土作用对一座位于Ⅲ类场地上的110 m三跨连续梁桥地震易损性曲线和震后通行能力的影响,首先建立墩底固结和考虑桩土作用2种有限元模型,选取50条实测的、符合工程场地条件的不同强度地震波作为输入,分别以桥墩墩顶和支座最大位移为目标响应,计算得到转角延性比和支座剪应变值,进而构建桥墩和支座的易损性曲线;然后通过宽界限法建立桥梁系统的地震易损性曲线,提出新的平均损伤水平值计算公式并结合易损性曲线评估该连续梁桥的震后通行能力。分析结果表明,同一地震强度下考虑桩土作用时的桥墩位移峰值比墩底固结情况大,更符合实际情况;对于桥梁构件易损性曲线而言,考虑桩土作用时支座破坏超越概率最大,但与墩底固结情况相比相差不大;采用桥梁系统地震易损性曲线评价桥梁交通流量变化更加合理,固结模型的震后交通流量评估Ⅲ类场地情况时不可忽略桩土作用对桥梁地震易损性的影响。
To determine the influence of pile-soil interaction on the seismic fragility curves and post-earthquake traffic capacity of a 110 m-long, three-span continuous girder bridge, two diffe-rent finite element models that consider fixed pier bottoms and the pile-soil interaction were constructed. Then, 50 seismic waves with different intensities were selected as excitation. The ducti-lity ratio of the rotation angle and the shear strain of the bearing were calculated with the maximum displacements of the pier top and bearing as the target responses. Subsequently, the seismic fragility curves of the entire bridge were established through the wide-bound method, and a new formula for the calculation of average damage level was developed to estimate the post-earthquake traffic capacity of the girder bridge. Analytical results demonstrate that under the same seismic intensity, the peak displacement of the pier under pile-soil interaction is larger than that estimated by the consolidation model, which better agrees with the practical situation. With respect to the fragility curves of bridge components, the maximum damage exceedance probability of the bearing occurs when the pile-soil interaction is considered, but is not large different from the situation of fixed pier bottoms. Changes in traffic flow can be reasonably evaluated by using the seismic fragility curves of the entire bridge system. However, the traffic capacity assessment given by the consolidation model is unsafe. This result implies that the influence of pile-soil interaction on the seismic fragility of bridges cannot be ignored in class-Ⅲ sites.

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