Finite-Element Modeling of Tubular Joints. II: Design Equations

Design equations for tubular joints are based on simplified analytical models that are modified by empirical constants to match test data. Their accuracy depends on the quality and number of test results that are available, and the range of their applicability depends on the assumptions used to derive their basic form. In a companion paper, finite-element modeling was used to perform a parametric study on the static strength of T-, DT-, Y- and X-joints when subjected to axial compression, axial tension, and in-plane bending moment. On the basis of the results, a new form for ultimate strength equations for tubular joints is derived using a modified version of the ring model. The new form is capable of modeling the increase in joint strength for joints with large branch to chord diameter ratios. The data from the numerical study is then used to develop specific design equations for joints under axial tension, axial compression, and in-plane bending moment.