Seismic performance of masonry-infilled RC frames with and without retrofit

This paper presents the findings of a research that focused on the seismic performance of masonry-infilled, nonductile, RC frames. This research has resulted in improved analytical methods and effective retrofit techniques to assess and enhance the performance of these structures. The methods were validated by a series of quasi-static tests conducted on one-story frame specimens as well as shake-table tests conducted on two 2/3-scale, three-story, two-bay, masonry-infilled, RC frames. This paper focuses on the observations from the shake-table tests and the further insight gained from a numerical study conducted with finite element models. The first shake-table test specimen had no retrofit measures, and the second had infill walls in the first and second stories strengthened with Engineered Cementitious Composite (ECC) and Fiber Reinforced Polymeric (FRP) overlays, respectively. The tests demonstrated the effectiveness of the retrofit measures. Finite element models that combine smeared and discrete cracks have been used in a numerical study to examine the benefits of the ECC retrofit and the influence of the capacity of the shear dowels that connect an ECC overlay to the RC beams on structural performance. It has been shown that these shear dowels play a critical role in enhancing both the strength and ductility of a retrofitted structure.