Influence of infill wall openings on pushover response of reinforced concrete moment resisting frame structures

In this study, the pushover behavior of reinforced concrete (RC) moment resisting frame structures with masonry infill walls having different opening percentages was investigated. The equivalent diagonal compression strut method was used to model the infill panels. The essential point in this method is the equivalent strut width. Firstly, five different expressions suggested by the researchers exist in the literature and one formulation given in a provision of FEMA 306 for calculating the width of compression diagonal strut were examined by analyzing 2, 4, 6 and 8 storey RC frames as full-infill frames. Then, various opening contents in infill walls have been studied. The openings in the walls were located at the center. The opening was formed at the percentages of 20, 40, 60, 80, and 100. A reduction coefficient proposed in the literature was adopted to find the equivalent width of the diagonal strut for the cases of the infill wall with opening. Thus, a total of 144 different RC frame models were evaluated through nonlinear static (pushover) analysis. The results on the capacity, initial stiffness, strength, and plastic hinge formation at mechanism as well as the energy dissipated by the buildings were discussed comparatively.