A comparison of punching shear strengthening of RC flat plates with FRP bars and steel bolts

This study investigated the behavior of carbon fiber-reinforced polymer (CFRP), aramid fiberreinforced polymer (AFRP) bars and steel bolts as post-installed shear reinforcements for strengthening flat plate structures to evaluate their cost and performance effectiveness via a series of monotonic load tests. Seven interior slab-column connections with a square column including one control specimen and six strengthened specimens with a single-line cruciform shear reinforcement were tested. Two shear reinforcement ratio conditions were examined, which comprised four and seven bars on each side of the column corresponding to 0.75 and 0.5 times the effective slab depth, respectively. The results were compared with the well-established design guidelines, revealing that the shear capacity of the specimens with post-installed shear reinforcement increased to a level where the failure mode changed from punching shear to flexure, resulting in more ductile behavior of the specimens. Additionally, the critical shear crack theory was used to characterize the performance of the specimens; the experimental results agreed well with the theory. The study indicated that FRP materials are competitive compared to the steel material.