In-Plane Loading Tests and a Retrofitting Technique for Masonry Infill Panels in RC Frames with Eccentric Openings

The use of masonry infills in reinforced concrete (RC)-framed structures implicates the strength of the frame and the seismic resistance of the building. The present study (1) experimentally investigated the behavior of masonry infill panels surrounded by RC frames with eccentric door openings, (2) proposed and evaluated a retrofitting method based on the experimental results, and (3) introduced an analytical masonry infill model that is currently used in seismic assessment for RC buildings in Taiwan. This study's retrofitting method centers on improving the confinement at the opening edge only instead of reinforcing the panel itself. Compared with existing methods, this method entails a lower retrofitting cost because a smaller area needs to be retrofitted. In experiments, the method notably improved the lateral resistance, where retrofitting yielded a 68% and 120% increase in strength in the push and pull directions, respectively. The confinement provided by the retrofit elements (1) allowed the damage on the panel to develop gradually; and (2) maintained the integrity of the panel during the test. Consequently, the drift at maximum strength significantly increased, and the panel could provide higher residual strength after a peak in strength. Although the deformation capacity was not improved because the retrofitting method did not alter the behavior of the columns, retrofitting yielded better energy dissipation due to a higher residual strength. Furthermore, the analytical masonry infill model generally agreed with the experimental data, although the displacements where the maximum strength occurred were underestimated and overestimated in the specimens with and without retrofitting, respectively.