Nonlinear finite element analysis of reinforced concrete masonry walls (CMU) subjected to in-plane monotonic loading

In this study, different masonry constitutive models in the compression and tension regimes under monotonic loading are compared and the best models are chosen in this study. These models are modified from a model used for concrete considering the similarities between concrete and masonry. A two-dimensional nonlinear finite element program employing the proposed masonry constitutive models was implemented to investigate the performance of reinforced masonry walls under in-plane monotonic loading. Experimental results from Shing, Ibrahim and Eikanas are used to verify the validity of constitutive model and the program. The comparison indicates the nonlinear constitutive model used to successfully model reinforced concrete behavior can be used with the same degree of accuracy to model reinforced masonry, especially for reinforced masonry walls with aspect ratios equal or greater than 1.0. The full loading, secant stiffness iteration method employing smeared rotating crack method was used, with convergence criteria set for both displacement and secant modulus. In addition, the general finite element software, ANSYS, was also used to simulate nonlinear static response of reinforced masonry walls under in-plane loading. Comparison of ANSYS results to experimental data indicated that this software is an effective tool for predicting cracking, reinforcement yielding, and ultimate load of reinforced masonry walls under in-plane monotonic loading. The load-displacement envelope ANSYS generates is close to the observed experimental curves. However both the nonlinear finite element program and ANSYS analysis can not accurately predict the behavior of the reinforced masonry walls with aspect ratios less than 1.0.