Predicting the strength of branch plate – RHS connections for punching shear

Abstract

The stress distribution in steel plates welded at right angles to either I-section or rectangular hollow section members is notoriously nonuniform, leading to early failure of the plate, tube wall, or weld. The paper proposes an upper-bound approach that combines lócal punching shear with normal yield line analysis. The resulting expression for strength and branch efficiency is seen to be sensitive to the value of tube wall slenderness, and in reasonable agreement with a previously obtained efficiency expression based on a lower bound to test results. The theory also confirms the experimental observation that the width ratio between the plate and the rectangular hollow section does not have a significant effect on the efficiency of the connection. The theory presented enables a parametric study of the joint strength and efficiency to be made, and thus leads to a greater understanding of the behaviour of joints to hollow steel sections.