Experimental in-plane seismic strengthening of masonry infilled reinforced concrete frames by engineered cementitious composites (ECC)

Abstract

Abstract The present study aimed to evaluate the performance of engineered cementitious composites (ECC) retrofit technique for unreinforced hollow clay brick masonry infill wall in non-ductile reinforced concrete (RC) frames subjected to in-plane cyclic loading (quasi-static loading). To this aim, the mechanical properties of ECC and masonry elements were tested. Then, four 1/3-scale, one-story, single-bay RC frames were fabricated. Among these specimens, one frame was tested without infill wall (BF), one frame with unretrofitted infill wall (IF-E0), and specimens IF-SF-E20 and IF-DF-E20-2 were retrofitted by using an overlay ECC on the masonry infill wall on one side and both sides, respectively. The retrofitted specimens provided higher lateral load capacity, stiffness, and energy dissipation capacity up to 215%, 32%, and 102%, respectively, compared to the unretrofitted specimen. Further, the proposed strengthening technique prevented brittle premature failure in the masonry infill walls and partially maintained the integrity of unreinforced infill walls. Also, the obtained backbone curves of specimens were idealized. Based on the results, the displacement ductility factor of the retrofitted specimens decreased up to 50%, but also the force reduction factor and the overstrength factor of them increased up to 19 and 68%, respectively. At the end of the paper, a simplified analytical method is proposed to calculate the peak strength of retrofitted masonry infilled RC frames. The results obtained from this method were close to the experimental results.