Assessment of robustness of reinforced concrete frame structures with masonry infill walls

Robustness of frame structures is fundamental to limit progressive collapse of buildings in case of accidental loss of columns. The interest in robustness assessment is growing in recent years especially for reinforced concrete structures, which are commonly analyzed considering the bare frame configuration. This paper presents a numerical study highlighting the influence of masonry infill walls on the robustness of reinforced concrete frame structures. The main geometrical and mechanical parameters identifying an infilled frame (aspect ratio, seismic detailing, lateral constrain degree) are investigated by performing parametric pushdown tests on reference two-bay frames extracted from different types of buildings. The tests are carried out by using a detailed finite element model of the infilled frame. Results show significantly different responses from bare and infilled frames in terms of resistance and displacement capacity under the different conditions tested. In a relevant a number of cases infills have shown to be fundamental to limit or avoid multiple collapses.