Recommendations for assessment and interpretation of the seismic capacity of URM walls with irregular opening layout from benchmarking different finite element models

Procedures, harmonized across modeling approaches, to check and interpret results are required when assessing the seismic capacity of unreinforced masonry (URM) structures, as demonstrated by the significant dispersion of predictions in benchmark tests representative of real practice. These procedures cannot be easily established because of large epistemic uncertainty. Therefore, the same assumptions on structural behavior and analysis method are imposed in recent benchmark exercises to limit uncertainty and foster procedures for result interpretation. In this context, this work aims to propose guided procedures for evaluating the pushover shear force–displacement response of URM walls and processing the corresponding results, based on the benchmark experience within the framework of 2022-2024 ReLUIS project (funded by the Italian Department of Civil Protection). These procedures were developed by comparing the predictions from four research groups using different finite element models. Walls with irregular opening layouts were selected as benchmark structures to understand the effect of irregularities in the wall response, namely in terms of crack propagation. The scale of a masonry pier is assumed as reference for initial model calibration in the procedure for evaluating the shear force–displacement response, and for sanity checks when processing results by using a graphical band domain method. The implications of the pier response calibration on the wall response are presented to show the sensitivity to input parameters. A multicriteria approach for near collapse limit state definition considering global and local response quantities is proposed. The key takeaways from the experience are eventually summarized as a set of warning-recommendations.