Limit Analysis of Ultimate Strength of Tubular X-Joints

Abstract

An investigation of the ultimate strength of tubular joints has been carried out in order to develop an analytical method that provides a rational basis for the design of tubular joints. In this paper, the ultimate strength of the axially loaded X-joints was evaluated using the yield line method. Two theoretical models based on the observed failure mechanism were presented. In the first model, it was considered that the ultimate strength is determined by the plastic moment capacity on the yield lines and the membrane action in the yield zone of the chord surface. The second model, which takes membrane action in the saddle region into account, was developed to predict the strength of X-joints when the ratio of brace to chord diameter approaches 1.0. The proposed theoretical models were successfully verified by comparing with the empirical formulas and the experimental results of 128 joint tests reported in the literature.