Initial axial stiffness of welded RHS T joints

Recently, CIDECT (International Committee for the Development and Study of Tubular Structures) has proposed the component method as a unified approach for the design of many types of connections, including welded tubular joints. Although CIDECT provides clear and simple equations for the resistance of welded tubular joints, the design of initial stiffness remains complicated and includes a number of uncertainties. This paper analyzes the theoretical approach for the initial axial stiffness of rectangular hollow section T joints. The validation against experimental data has shown that the component method considerably overestimates the stiffness of T joints. The paper develops new equations for the stiffness of the components “chord face in bending” and “chord side walls in compression”. The equations are based on simplified mechanical models, employing finite element analyses to calculate the parameters for which analytical solutions are found extremely complicated. In addition, the article numerically investigates the effect of chord axial stresses on the axial stiffness of joints and proposes a corresponding chord stress function.