Study on in-plane/out-of-plane seismic performance of masonry-infilled RC frame with openings and a new type of flexible connection

The seismic performance of masonry-infilled reinforce concrete (RC) frame buildings is an intricate issue due to the variety and complexity failure mechanisms observed on this type of buildings during an earthquake, mainly due to wall-frame interaction. This leads to seriously damaged infill walls and it can produce large economic losses and even jeopardize human lives in an earthquake event. For this reason, in this study a new type of flexible connection able to reduce the wall-frame interaction, and consequently improving the overall seismic performance of the structure is examined. The research encompasses both experimental and numerical analyses of three distinct cases: a rigid connection (Case 1), a traditionally flexible connection (Case 2), and the new proposed type of flexible connection (Case 3). The in-plane and out-of-plane seismic performance is analyzed and compared for these cases. As a result of the study, the new type of flexible connection effectively reduced in-plane damage of the infill walls and minimized undesirable infill-frame interaction. Compared with rigid and traditional connections, the energy dissipation capacity increased by 37.7% and 3.5% for the masonry-infilled RC frame structure with a new flexible connection. At the same time, the out-of-plane strength and stiffness of the new flexible connection increased by 119.8% and 104.2% in the same prior in-plane drift ratio than that of traditional flexible connection. It is concluded that the steel cable structure (the U-bars are connected to the frames to ensure out-of-plane stability of infill walls.) can improve the restraint of frames on infill walls, which is beneficial to development of out-of-plane horizontal arch mechanism.