Behavior and vulnerability of reinforced masonry shear walls

The overarching goal of the research presented herein was to establish the key behavior mechanisms and seismic vulnerabilities of reinforced masonry (RM) shear walls. Currently, there are knowledge gaps related to partially grouted masonry shear walls, regarding their failure mechanisms, applicability of current code provisions to PG walls, and influence of bidirectional loading on the behavior of such walls. To bridge these gaps a research program that integrated both experimental and analytical approaches was conducted. The centerpiece of the experimental program was a series of full-scale, quasistatic cyclic tests of both PG and FG masonry shear walls. Key test parameters included the level of vertical stress, wall aspect ratio, and mortar formulation. Following these experiments a series of nonlinear finite element models were developed and correlated with the experimental results. These models were then used to examine the influence of bi-directional loading through a series of parametric studies with out-of-plane drift, wall aspect ratio and vertical stress as variables. Results of this study indicated a potentially significant seismic vulnerability of PG masonry shear walls that is not reflected in current design provisions. The PG masonry shear walls tested displayed shear strengths less than half of the capacity estimated by current design methods. The modeling component of this research developed an efficient nonlinear finite element modeling approach that proved capable of simulating the capacity (within 10%), failure modes and hysteretic response of both PG and FG masonry shear walls. This modeling approach was also validated for the prediction of out-of-plane response, and then used to examine the bidirectional response of PG masonry shear walls. Results from this study indicated that out-of-plane drifts corresponding to the collapse prevention limit state may reduce the inplane capacity of PG walls by more than 20%. Although the capacity of PG walls is influenced by out-of-plane drifts, their hysteretic responses, and in particular, energy dissipation and ductility capacities remain nearly unchanged. As a result, the seismic response of PG masonry walls is likely only nominally affected by bi-directional ground motions.