Seismic upgrading of infilled RC frames having low concrete strength using engineered composites under cyclic and axial loading

In this study, six reinforced concrete (RC) frame specimens with low concrete strength were exposed to reversible lateral cyclic loading and axial loading. One of these frames was bare, one with infill walls, and the remaining four were infilled specimens strengthened using a cementitious matrix grid (CMG). With the tests, the specimens were observed from the first loading to the collapse state and the base shear force-peak displacement relationship and total absorbed energy were determined. Comparison based on the bare frame showed that the maximum lateral load capacity of the infilled frame increased by 112 % and CMG-strengthened specimens displayed varying improvements of 190-250 %. According to a comparison based on the infilled specimen (without CMG), the maximum lateral load capacity of CMG-strengthened specimens increased by 37-66 %. In terms of total energy absorption, infilled frame increased by 31 % and CMG-strengthened specimens exhibited improvements up to 335 % compared to the bare frame. According to the infilled specimen (without CMG), CMG-strengthened specimens displayed reductions of 17-31 % in total energy absorption except specimen 2b. The obtained results revealed that strengthening both sides of the infilled RC frame using double layer CMG with anchorages was found to be the effective strengthening practice in terms of maximum load capacity, energy dissipation and ductility. Furthermore, the test results showed that infill walls considerably increased the shear strength and stiffness of the RC frames.