UC San Diego

Reinforced masonry (RM) structures are commonly found in North America including in areas of high seismicity. However, the ability of such buildings to meet the performance expectations of design codes for high-intensity earthquakes has not been thoroughly validated at the system level. Furthermore, the seismic behavior of partially grouted masonry (PGM) wall systems is not well understood. In this study, a detailed finite element (FE) analysis framework has been developed to simulate the seismic response of RM structures through collapse. The framework combines smeared-crack shell elements and cohesive-crack interface elements to capture the fracture of masonry, and beam elements to simulate the nonlinear behavior of reinforcing bars. The strain penetration and dowel action that may develop in the reinforcing bars are also accounted for. To enhance robustness and accuracy, an element removal scheme has been introduced. This scheme is triggered in the event of reinforcement rupture or severe masonry crushing. The material models and interface elements have been implemented in a commercial program. The modeling scheme has been validated with experimental data from quasi-static and shake-table tests, and has been used to provide insight into the seismic resistance mechanisms of reinforced masonry structures and the influence of design details on their seismic performance.

Two full-scale shake-table tests were conducted to acquire a better understanding of the seismic performance of PGM wall systems. The first structure had design details that represent the current practice, while the second had improved design details including stronger vertical grouted elements and bed-joint reinforcement. It has been shown that the PGM structure constructed according to current practice could develop an adequate base-shear capacity but failed in a brittle manner, while the improved design details studied could enhance the ductility and shear capacity of the structure. The FE modeling scheme has been extended for analyzing PGM and has been validated with data from the two shake-table tests and quasi-static tests. The models are used to understand the distribution of lateral forces among the wall components of the two test structures, and to evaluate the shear-strength equation given in the design code. The code equation has been found to be adequate for these structures. A parametric study has been conducted to demonstrate the beneficial influence of continuous bond beams below window openings, double vertical grouted cells, and joint reinforcement on the seismic performance of a PGM structure.