Finite element modeling of nonrectangular reinforced concrete structural walls

Abstract

This study employs and extends the Fixed-Angle-Strut Finite Element (FSAFE) model towards simulating the hysteretic response of the nonrectangular reinforced concrete structural walls subjected to multidirectional lateral loading. The FSAFE model, which was previously developed and validated for planar walls, is a relatively simple finite element model formulation based on a fixed crack angle modeling approach for concrete. The model also incorporates constitutive relationships for shear-aggregate interlock behavior along crack surfaces, and dowel action on reinforcing steel bars. Within the scope of this study, the FSAFE model formulation is extended to walls with nonrectangular cross-sections. As well, a new solution strategy is developed in order to enable nonlinear analysis of such walls under biaxial lateral loading conditions. Furthermore, the model is improved by incorporating reinforcement buckling behavior into its formulation. Model predictions are compared with experimental data on four densely instrumented U-shaped walls specimens available in the literature, at various global and local response levels. The U-shaped wall specimens investigated differ in terms of the loading scheme applied during testing (sweep pattern vs. diagonal), as well as the reinforcement configurations (concentrated at boundaries vs. distributed along web), axial load ratios, and reinforcement ratios. Comparison of lateral load vs. top displacement responses of the walls reveals good correlation between the analytical and experimental results. The model well-captures the lateral load capacity and lateral stiffness of the wall specimens, as well as their cyclic response characteristics including pinching behavior, stiffness degradation, and residual displacements. In terms of local deformation responses, including the contribution of flexural and shear deformations to wall top displacements and the distribution of vertical strains across wall base and along wall height, the model provides reasonable estimates for most cases.