Strength evaluation of x-joints internally stiffened with longitudinal diaphragms

Abstract

X-joints on the launch-legs are usually reinforced using thicker can section, internal ring stiffeners or external plate gussets to increase the load carrying capacity and to circumvent fabrication limits. In this paper, an alternative stiffening arrangement for a uniplanar X-joints is proposed, in which the chord member is internally stiffened with longitudinal diaphragm. The diaphragm provides a direct load path to transfer the brace loads and thus enhances the basis strength of the `simple joint' and will be less complex to fabricate than a ring-stiffed joint. The ABAQUS software is used for strength computations and its accuracy is verified against referenced test and numerical results. It is found that there is significant strength enhancement for a X-joint reinforced by a longitudinal diaphragm, with an associated reduction in material requirements as compared to a joint reinforced by a can.