An improved cyclic softened membrane model (ICSMM) based smeared reinforced concrete (RC) plane stress element has been developed in the present study. The newly developed two-dimensional (2D) element has been implemented in the OpenSEES nonlinear finite element analysis (NLFEA) framework. The effectiveness of the developed element has been thoroughly validated using experimental results of three RC panels tested under cyclic pure shear loading and three hollow rectangular RC (HRRC) bridge piers tested under static axial and reversed cyclic in-plane bending loads. The accuracy of the NLFEA model based on ICSMM based plane stress elements has been further verified with the results obtained from the simulation of the considered test specimens using the NLFEA model based on existing CSMM based plane stress elements. After thorough validation ICSMM based NLFEA model has been used to perform incremental dynamic analysis (IDA) and develop seismic fragility curves for the three considered HRRC bridge piers using maximum likelihood estimation (MLE) method. The robustness of the fragility curves, thus obtained have also been verified by comparing with the fragility curves of the same bridge piers developed using two commonly used one dimensional (1D) NLFEA models based on fiber-beam-column elements that can capture axial-flexure and axial-shear-flexure interactions. The advantages and disadvantages of using ICSMM based NLFEA model over 1D fiber based NLFEA models for seismic fragility assessments have also been presented. It has been concluded from the results obtained that the ICSMM based NLFEA model is very effective to assess the complete nonlinear response of HRRC bridge piers under both in-plane reversed cyclic and seismic loads compared to the existing CSMM based 2D model and two other widely used 1D simulation models.

在本研究中开发了一种改进的循环软化膜模型 (ICSMM) 基于涂抹钢筋混凝土 (RC) 平面应力元素。新开发的二维 (2D) 单元已在 OpenSEES 非线性有限元分析 (NLFEA) 框架中实施。使用在循环纯剪切载荷下测试的三个 RC 面板和在静态轴向和反向循环平面内弯曲载荷下测试的三个空心矩形 RC (HRRC) 桥墩的实验结果，已彻底验证了开发元件的有效性。基于基于 ICSMM 的平面应力元素的 NLFEA 模型的准确性已通过使用基于现有 CSMM 平面应力元素的 NLFEA 模型对所考虑的试样进行模拟所获得的结果得到进一步验证。经过彻底验证后，基于 ICSMM 的 NLFEA 模型已被用于执行增量动力分析 (IDA)，并使用最大似然估计 (MLE) 方法为三个考虑的 HRRC 桥墩开发地震易损性曲线。通过与使用两种常用的一维 (1D) NLFEA 模型开发的相同桥墩的易损性曲线进行比较，由此获得的易损性曲线的稳健性也得到了验证，该模型基于可以捕获轴向弯曲的纤维-梁-柱单元和轴向剪切弯曲相互作用。还介绍了使用基于 ICSMM 的 NLFEA 模型而不是基于 1D 光纤的 NLFEA 模型进行地震脆性评估的优缺点。