Fillet weld effective lengths in CHS X-connections. II: Finite element modelling, parametric study and design

Finite element (FE) modelling was performed to extend the results of a recently completed experimental test program to evaluate the static strength of fillet welds in X-connections between circular hollow sections (CHS). Non-linear FE models with weld fracture were validated by comparison of spot strains, load-deformation response, and fracture load with 12 experimental tests. Two hundred and fifty-six FE weld-critical CHS-to-CHS X-connections, with varied branch-to-chord diameter ratio, chord wall slenderness, branch inclination angle, and branch-to-chord thickness ratio, were analysed under quasi-static branch tension. The effect of these parameters on fillet weld strength is illustrated, and the structural reliability (or safety index) of North American specification provisions for weld effective lengths is confirmed. An alternative method for estimating fillet weld strength, with specific weld effective lengths, is proposed. Recommendations for a new design approach that meets the minimum target safety index in North America are made.