Effective strengthening of RC frames with and without lap splice problems

A series of tests were performed at ITU Earthquake and Structural Engineering Laboratory, for examining strengthening of poorly designed brittle brick infilled RC frame specimens by carbon fiber reinforced polymer (CFRP) composite fabrics. The aim of this experimental work was to reach an effective and economical strengthening technique without causing excessive disturbance to occupants. Seven 1/2 scale two story-one bay RC frames were tested under constant vertical load and reversed cyclic lateral loads. First three specimens were constructed with inadequate lap splices of longitudinal reinforcement of the columns at first and second story levels. The other four specimens were constructed with continuous longitudinal column reinforcement without any lap splicing problem. Each group of specimens included one reference bare frame, one infilled frame and one or two infilled frame specimens strengthened by CFRP fabrics. Two different methods were used for strengthening. For the first one, one ply of CFRP fabrics were pasted by epoxy over two diagonal directions of infill walls on both sides, while for the second method two plies of CFRP fabrics were applied only on one side of the specimens. Test results were evaluated in terms of lateral load capacities, stiffnesses and failure mechanisms. It is concluded that strengthening of the infill walls by applying CFRP composites in diagonal directions, provides significant enhancement in lateral strength and stiffness.