Experimental evaluation of RC beams defected in both concrete strength and steel reinforcement and retrofitted by fiber reinforced polymers

摘要

Insufficient reinforcement lap-splice is one of the defects, which negatively affect the structural behaviour of reinforced concrete beams. Experimental investigation was carried out to study the efficiency of transverse FRP sheets on enhancing the structural behaviour of RC beams that had defected lap splice zones with normal and low concrete strength. Eight RC rectangular beams were tested in positive bending, four of them were strengthened by transverse FRP wraps in the defected lap splice region and the other four beams were kept unstrengthened and considered as control specimens. The main parameters were concrete compressive strength, type of FRP sheets and the retrofitting length as a percentage of the defected lap splice length. The cracking behaviour, failure modes, load-deflection relationships and the strains in longitudinal steel were investigated. It was concluded that the transverse FRP confining system provided a new mechanism whereby most bars over the spliced region could be used more effectively in the stress transfer between steel and concrete leading to a more ductile failure mode combined with a noticeable increase in the ultimate load.