Multi-strut and empirical formula-based macro modeling for masonry infilled RC frames

It is widely accepted that infill walls play an important role in the structural response of buildings under seismic excitations. Disregarding their influences on the seismic design and evaluation of structures could be potentially dangerous. Therefore, a reliable numerical model is necessary. Because of its simplicity and efficiency, the equivalent strut model is the most widely used to represent infilled frames. In this study, a novel multi-strut macro model and associated empirical formulas for modeling infilled RC frames are proposed. The model was developed based on previous experimental observations. Fiber-section truss elements are used as the struts. All potential failure modes of the infill wall were considered by means of the equivalent stress–strain parameters of the struts. Empirical formulas for predicting these equivalent stress–strain parameters were developed and calibrated based on a comprehensive experimental database and regression analysis. Finally, blind validation tests of the proposed model and empirical formulas were performed to assess their reliability. Monotonic and cyclic load simulations of the infilled RC frames were carried out and compared with experimental results. The application of the proposed approach for both single-bay and multi-bay infilled frame simulations was examined.