FEM analysis of CHS X-joints on the effect of out-of - plane bending performance

The out-of-plane bending performance of unstiffened X-joints with similar brace and chord diameters are studied, and the influence of brace inclination angles, axial stress and diameter-thickness ratio of chord on failure mode, ultimate bearing capacity and flexural rigidity of tubular joints are discussed in this paper. The results indicate that failure mode for X-joints with high brace-to-chord diameter ratios, which yielding area first be found around the chord wall between the two saddle points and then expand to intersecting lines, is different from joints with low diameter ratios. It is obvious that tubular joints show characteristics of semi-rigid connection, its plastic zone develop relatively full under lager bending and thus reflect plastic hinge feature. It can be found that a larger brace inclination angles could increase the ultimate capacity of X-joints, but decrease its flexural rigidity. What´s more, axial pressure and tension in chords could weaken the rigidity and bearing capacity of X-joints, and an over larger pressure can lower the ductility of X-joints. At last, by comparing non dimensionalized moments, the paper points out that it is not reasonable to use geometrical factor just considering chord radius-thickness ratio.