New headed reinforcements for RC exterior beam-to-column joints. Experimental and numerical simulation

In severe intensity seismic zones, the conventional detailing of reinforcement in the exterior beam-to-column joint causes congestion of steel that affects the ease of construction. This article evaluates the behaviour of exterior beam-column joints with different anchorage/connection methods suitable for avoiding steel congestion. Sub-assemblages having six-joint connections were cast and tested under reverse cyclic loading at the tip of the beam under displacement control. Of these, four connections are non-conventional reinforcement detailing were detailed as per ACI 352R-02 and IS-456 along with confinement as per IS-13920, Straight-Headed Bar, X Cross-Headed Bar and the remaining specimens are detailed as a conventional confined specimen. The experimental results from the specimens with different anchorages are compared with the monolithic connection. The study revealed that the X cross-headed bar considerably enhanced the joint's seismic performance in terms of strength, ductility, and energy dissipation. A numerical model (ABAQUS) that considers the nonlinear behaviour of steel and concrete in the beam-column joint is also considered in this study. The results of the experimental tests and the numerical differed by less than 10% on average. The developed headed-bar connection at the beam-column joint is evaluated by calculating the possible shear stress in the joints theoretically and the estimated values lie well within the values specified in standards/codes.