Seismic design method for preventing column shear failure in reinforced concrete frames with infill walls

The presence of masonry walls has a significant effect on the seismic response of structures. The infill panels can increase the overall lateral stiffness and strength of structures. This increase in strength and stiffness is normally beneficial to the overall seismic resistance unless the presence of masonry walls creates an irregularity in the structure or the infill-frame interaction induces excessive forces in the frame, leading to local failure. This study evaluated a proposed design method to prevent local shear failure of RC columns due to infill-frame interactions. The proposed method is based on local plastic mechanism analysis of the column considering the variation in the column shear demand and column shear capacity at different deformation states. Simplified equations based on the equivalent strut concept together with finite element analysis (FEA) are used to determine the demand of the surrounding frame due to infill-frame interaction and to assess key response parameters for the design. An RC frame with a concrete block masonry wall was designed with the proposed method and tested under cyclic loading. The test showed that local failure of the surrounding frame could be prevented, resulting in a ductile behavior. Only horizontal cracks were observed at the ends of the frame members, indicating only the flexural yielding. Finally, since a large variation in the infill wall strength may exist, the implementation and limitations of the method are also discussed.