Seismic performance of hybrid RC frame-masonry structures based on shaking table testing

Abstract

Hybrid reinforced frame-masonry (HFM) building structures are widely used in China and East Asia. However, they have been observed to sustain significant damage during recent earthquakes, where the confined masonry elements incur severe failures while the frame elements remain largely intact. This failure phenomenon results from the simplification of HFM structures as frame-only systems in seismic design, which neglects the actual behavior and failure mechanisms of these structures. To address this issue, a 1/4 scale specimen representing a typical HFM structure was tested on shaking table to analyze its seismic behavior. The experimental results indicate that, when subjected to seismic events, the confined masonry components fail in shear at relatively small displacements, which leads to a substantial reduction in the lateral stiffness of the structure. Subsequently, damage is observed in the frame columns and transverse infill walls, ultimately culminating in collapse once the transverse walls incur severe damage. At a 0.2 g ground acceleration, the seismic shear force in the confined masonry grid was found to be 63 times greater than that in the frame grid. At 0.5 g ground acceleration, the frame and masonry grids exhibited similar lateral displacement phases. This indicates that, despite misalignment between the center of stiffness and center of mass, the torsional effects were greatly constrained by the transverse walls. Based on these findings, it is recommended that the lateral load-resisting components of HFM structures be defined by their damage states, rather than by column grid divisions alone. These results provide valuable insights into the seismic vulnerability and failure mechanisms of HFM structures, highlighting the need for improved seismic assessment and design methods.