Estimation of shear strength of RC interior beam-column connections based on the strut model

Abstract

This paper presents a new theoretical macro model developed for estimation of joint shear strength of RC interior beam column connections. In the model, a compressive strut is considered as failing in bending mode. Hence, the stress block concept based on the beam bending theory may be used to estimate the strut strength. The depth of compressive strut is calculated from the neutral axes in the beams and columns, which are derived from the bending theory considering axial forces in the connected members and the effect of transverse reinforcement bars in the joint panel. Finite element analyses were carried out in order to observe the behavior of the compressive struts. Analysis results showed that the process of the formation and disappearance of the strut is consistent with the adoption of the bending theory in the strut model. The joint shear strengths of specimens in a database collected from past RC beam-column joint experimental studies were calculated by the developed model and compared to the published experimental values. The results show that the model provides a theoretical explanation of joint behavior as well as a much more improved estimation than the methods currently recommended in both the ACT or AIJ codes.