External Reinforced Concrete Beam-Column Joints: Experimental Investigation, Analytical Prediction, and Simple Design Suggestions

Experimental research was carried out regarding the flexural behavior of three full-scale external beam-column concrete joints cast with plain concrete in the presence of shear reinforcements in the joint regions constituted by horizontal and/or vertical stirrups and subjected to cyclic load reversals. Three specimens were designed to fail in the joint region. One had only one stirrup in the joint; another was confined with three horizontal stirrups in the joint; and one additional specimen had three horizontal and three vertical stirrups. The experimental results show that it is also possible to increase the shear strength of the joint regions and the bond strength of longitudinal bars of beams under cyclic reversal actions. From the analytical point of view, a simple model based on the limit state due to concrete crushing with horizontal and vertical transverse stirrups in both the elastic and plastic states was proposed with good prediction of experimental results and good results in comparison with other existing analytical expressions for shear strength prediction of joint regions. The original contribution of the research is to consider the concrete confinement of a strut member and its interaction with horizontal and vertical stirrups in the prediction of shear strength of a joint region.