考虑不确定性公路CFST拱桥抗倒塌安全储备分析

An Analysis on Collapse Margin for Highway CFST Arch Bridge Considering Uncertainty

为研究在不确定性影响下桥梁结构抗倒塌安全储备能力和地震损失,提出基于构件破坏安全储备系数DMR求取桥梁抗倒塌安全储备系数CMR的分析方法,并以此方法评估结构遭遇地震时的损失情况。以某公路CFST拱桥为例,首先充分考虑了模型信息相关不确性,利用拉丁超立方抽样,对模型信息参数进行随机组合,采用OpenSees程序对随机组合参数建立算例拱桥弹塑性动力分析模型,进行非线性时程分析,再利用概率地震需求分析(PSDA)方法建立构件概率地震需求模型,确定连续地震作用下构件易损性曲线,通过分析不同主要承重构件在遭遇地震时的破坏情况来最终确定桥梁的易损性曲线,探究DMR、CMR、地震损失、不确定性4者之间关系。通过对比两种不确定性工况分析,结果表明:不确定性对CMR、DMR和地震损失评估有着重要影响。在给定地震动强度作用下,DMR随着不确定性增大而变小,造成构件地震损失的增大。在同等地震下,DMR较小的构件比DMR较大的构件更易发生破坏。因桥梁结构的CMR是由DMR求得,所以在不确定性影响下变化趋势与DMR一致。通过构件的破坏安全储备进行评估,在评估过程中充分考虑不确定性的影响有助于更加精准了解结构的抗倒塌安全储备能力以及在遭遇地震时的损失情况。

In order to study the collapse margin capacity and earthquake loss of bridge structure based on the influence of uncertainty,an analysis method is proposed to calculate the bridge collapse margin ratio(CMR)based on the member damage margin ratio(DMR),and this method is used to evaluate the loss of the structure in the event of earthquake.Taking a highway CFST arch bridge as an example,firstly,the uncertainty of the model information is fully considered,and the Latin hypercube sampling is used to combine the model information parameters randomly.The OpenSees program is used to establish the elastic-plastic dynamic analysis model for arch bridge,and the nonlinear time-history analysis is carried out.Then the probabilistic seismic demand model of components is established by using probabilistic seismic demand analysis(PSDA)method.The vulnerability curve of components under continuous earthquake is determined,the vulnerability curve of the bridge is finally determined by analyzing the damage of different main loadbearing members in the event of earthquake,and the relationships among DMR,CMR,earthquake loss and uncertainty is explored.By comparing the 2 working conditions with different uncertainty,the result shows that(1)uncertainty has an important impact on CMR,DMR and earthquake loss assessment;(2)under the action of a given ground motion intensity,the DMR decreases with the uncertainty increase,resulting in an increase in the seismic loss of the component;(3)under the same earthquake,the components with smaller DMR are more likely to be destroyed than those with larger DMR;(4)under the influence of uncertainty,the change trend is consistent with that of DMR,because the CMR of bridge structure is obtained by DMR.Through the evaluation of DMR of members,fully considering the influence of uncertainty in the evaluation process is helpful to more accurately understand the collapse margin capacity of the structure and the loss in the event of earthquake.