Effect of infill walls on behavior of reinforced concrete special moment frames under seismic sequences

This study investigated into the effect of infill walls on behavior of reinforced-concrete (RC) special moment frames subjected to multiple earthquakes. For this purpose, 4, 8 and 12-storey RC frames in three cases of inclusion and exclusion of infill walls as well as inclusion of infill walls with openings are analyzed using OpenSees software. The nonlinear static and dynamic analyses are carried out on the models and for dynamic analyses, 20 main and aftershocks are taken into account. Accordingly, strength and stiffness of the structures are determined using nonlinear static (pushover) analysis and structural responses such as displacement ductility, rotational ductility and energy absorption are obtained from nonlinear dynamic analyses. The results indicate that inclusion of infill walls, increases stiffness and ultimate strength of the structure, but to the contrary, ductility and energy absorption are reduced. Among all models, the structures including infill walls, incurred intense strength loss owing to cracking and destruction of the infill walls. Comparison of results of the main shocks and aftershocks illustrates that contribution of the aftershocks, has raised the responses by 20-100% highlighting importance of aftershocks particularly for the structures with infill walls.