基于JC法的近场地震作用下钢筋混凝土高墩塑性铰形成概率分析

为研究近场地震动作用下钢筋混凝土(RC)高墩塑性铰形成概率。以高度为90m的某RC高墩为研究对象,首先采用支持向量机算法预测截面等效屈服曲率;然后考虑墩身参数和近场地震动的随机性,采用OpenSees建立高墩模型,并进行增量动力非线性分析;最后以等效屈服曲率为临界指标,采用JC法对截面动力响应当量正态化后,计算分析截面塑性铰形成概率。研究结果表明:RC高墩截面顺桥向和横桥向等效屈服曲率均具有明显的离散性且服从正态分布;顺桥向近场地震作用下,墩底和墩身中部区域塑性铰形成概率均较大并形成塑性铰,且墩身中部塑性铰长度达31.7m,比只考虑地震动随机性确定的塑性铰区域长度大84.3%,而横桥向仅墩底区域塑性铰形成概率较大且与只考虑地震动随机性确定的塑性铰区域长度基本一致。塑性铰形成概率分析法,可以更加准确地对RC高墩的塑性铰形成和分布做出评估。

Probability analysis for plastic hinge formation of a RC high pier under near-field seismic action based on JC method

In order to study probability of plastic hinge formation of a reinforced concrete (RC) high pier under near-field seismic action, a certain RC high pier with a height of 90m was taken as the study object. Firstly, the support vector machine algorithm was used to predict the equivalent yield curvature of its cross section. Then, considering pier parameters and the randomness of near-field seismic action, the software OpenSees was used to build the high pier model to do the increment dynamic nonlinear analysis. Finally, the equivalent yield curvature was taken as the critical index, and dynamic responses of the pier’s cross section were equivalently normalized with JC method to calculate and analyze the probability of plastic hinge formation of the pier’s cross section. The results showed that equivalent yield curvature of RC high pier cross section in forward bridge direction and that in transverse bridge one have obvious discreteness and obey normal distribution;under near-field seismic action in forward bridge direction, probabilities of plastic hinge formation in pier bottom area and pier middle part are larger to form plastic hinges, plastic hinge length in pier middle part is 31.7m and 84.3% longer than that determined only considering the randomness of seismic action;under the near-field seismic action in transverse bridge direction, probability of plastic hinge formation in pier bottom area is larger, and plastic hinge length is basically consistent to that determined only considering the randomness of seismic action;the probability analysis method for plastic hinge formation can be used to more accurately evaluate plastic hinge formation and distribution of RC high-piers.