The static strength of multiplanar tubular TX-joints under axial loading excluding the effects of overall chord bending moments

Abstract

Since no experimental data exist for multiplanar TX-joints, non-linear FE analyses are carried out on axially loaded multiplanar TX-joints in order to study the local static behaviour of this type of joint (i.e. excluding the effects of overall chord bending moments at the intersection between the chord and the braces). The influence of the chord length parameter α has been excluded by applying compensating moments to the chord ends. The individual influences of the geometric parameters β and 2 γ and the load ratio J (=load on out-of-plane braces divided by the load on the in-plane brace) on the static strength are made clear. In addition, the effects on the joint behaviour due to different end conditions of the out-of-plane braces (i.e. the out-of-plane braces were either free or restrained against rotations) are shown for various β values. Based on the FE results and the expressions derived from the analytical `ring model' approach, ultimate strength formulae are established for the local strength of multiplanar TX-joints with J=0.0 and ∞. Based on the numerical results of the TX-joints subjected to load ratios J different from 0.0 and ∞, another set of two equations is developed describing the multiplanar interaction effects for axially loaded multiplanar TX-joints excluding the influences of overall chord bending moments.