Recommendations for Seismic Evaluation and Retrofit of Low-Rise URM Structures

Based on the results of a full-scale lateral load test of a two-story unreinforced masonry (URM) structure, modifications are suggested for the model implied by FEMA 356 for the in-plane analysis of perforated URM walls. These modifications allow the model to address global issues such as flange participation, overturning effects, and global rocking. In addition, changes are proposed to the pier model as well as to the definition of effective pier height. Following a description of each modification, the analysis results obtained using the proposed model and FEMA 356 are compared with experimental results. In terms of base shear resistance, the proposed model displayed an average error (absolute value) of 13% compared with an average error of 21% from FEMA 356. In addition, the proposed model also provided more accurate representation of failure modes. The improved accuracy of the proposed model is primarily attributed to the consideration of global issues. The results of a parametric analysis are also presented to provide insight into the relative influence of each modification proposed.