Behaviour of exterior beam column joints with coupled reinforcement

Abstract

Exterior corner beam column joint is a critical region in reinforced concrete structures where through it, large stresses to and from the adjoining members are transferred. The breakdown of this joint always causes a failure of the structure, as well it is very difficult to repair this joint compared to any other structural element. Many structural problems arising in the knee joint, such as deficiencies in mechanical properties due to rebar cold bending and the problems of congestion of the joints as a result of the splicing of the reinforcing bars. In order to overcome these problems, the present study examined the structural behavior of knee joint, subjected to closing quasi-static loads, with new use of L-shaped mechanical coupler to connect the perpendicular main tension reinforcing bars instead of bending it or splicing the rebars. Eight full-scale specimens divided into four groups were tested. Each group consists of two specimens, a conventional and a proposed reinforcement detail specimen. The parameters also include the effect of concrete grade and presence of horizontal and vertical stirrups in the knee joint. The results of this study showed that, with the use of L-shaped mechanical coupler, significant increase in ductility, efficiency, performance and load carrying capacities were occurred.