Influence of Masonry Infill on the Linear Seismic Response of Reinforced Concrete Frame

The present study involves a comparison of the linear seismic responses of reinforced concrete frame structures. These responses result from two different modeling approaches for masonry infill walls: one employing a single equivalent diagonal strut, and the other following the guidelines of the current Algerian seismic code (RPA99/version 2003). The latter considers the infill wall stiffness solely through the global behavior coefficient R, without introducing any diagonal strut. Using the SAP2000 software, modal analyses with respect to the Algerian response spectrum were conducted on various three-dimensional (3D) Gf+6 story building models. These models included: (1) a bare frame, (2) a frame with infill panels extending throughout the height, and (3) frame models with infill panels and a flexible floor located at various levels of the structure. Various response parameters, such as fundamental natural periods, floor displacements, inter-story displacements, P-Δ effects, shear forces, and bending moments at different floors, were computed for all considered configurations and presented in a comparative manner. The results obtained from the models employing the equivalent diagonal strut significantly deviate from those obtained using the current Algerian seismic code. The latter yields result that do not accurately reflect the influence of infill walls on the overall structural behavior when subjected to lateral forces. These findings underscore the importance and necessity of incorporating the modeling of infill wall effects using an equivalent diagonal strut in the current Algerian seismic code.