CSMM based seismic fragility analysis of shear dominant RC hollow rectangular bridge piers

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.