Experimental study on the progressive collapse performance of RC frames with infill walls

• Study progressive collapse of frames with or without infill walls by experiment.
• Infill walls enhance maximum resistance but reduce ductility of frames.
• Infill walls change strains distributions in beams.
• Infill walls change the cracks development and failure mode of the frames.
• Failure mechanisms of the two frames were proposed.

The interaction between the infill walls and the reinforced concrete (RC) frame members in the progressive collapse process was examined experimentally in this study. Two 1/3 scaled, four-bay, two-story RC frame specimens, one of which was featured without infill walls while the other with infill walls, were tested. The frame specimens were designed in such a way that the center column of the first story was missing, in order to simulate the failure of the structural component due to abnormal loads or design flaws. The frame specimens were quasi-statically pushed downward at the top of center column under displacement control to investigate the progressive collapse mechanism of the RC frames, with a focus on the effects of infill walls. Specifically, the physical quantities and phenomena of great interest in this study include the collapse resistance force and mechanism, strain variation and crack development in structural components, and local and global failure modes of the frames. The test results showed that the infill walls can provide alternative load paths for transferring the loads originally only supported by the beams, and thus, improve the collapse resistance capacity of the RC frame. The infill walls, however, may reduce the ductility of the RC frame and may change the failure mode of the frame. It is concluded that the infill walls may affect (i.e., either improve or impair) the performance of RC frames against progressive collapse in different aspects.