ADVANCES IN WELD DESIGN FOR HOLLOW STRUCTURAL SECTION CONNECTIONS

Abstract

A research program involving experimental and finite element (FE) analyses was conducted to investigate effective geometric properties for the design of welds in hollow structural section (HSS) connections as “fit-for-purpose”. The reliability of weld effective length, le, formulae for welds in rectangular hollow section (RHS) and circular hollow section (CHS) connections was examined, and new design formulae for fillet and partial joint penetration (PJP)-groove welds were recommended. Experimental data from tests on RHS gapped-K, overlapped-K, T-, Y-, and X-connections under branch axial load(s) were analysed to assess the reliability of fit-for-purpose weld design in accordance with the European design code, prEN 1993-1-8:2021. Existing le formulae were evaluated in conjunction with the Directional and Simplified Methods of prEN 1993-1-8:2021, and minimum fillet weld throat thicknesses, tw, required to develop the capacity of a connected RHS branch were recommended. An experimental program was then conducted on PJP-groove welds in six transverse plate-to-CHS X-connections to verify new le formulae. Reliability analyses were conducted and design recommendations for fit-for-purpose welds in plate-to-CHS X-connections were provided in accordance with North American design codes (AISC 360-22 and CSA W59:24). An assessment of micromechanics-based ductile fracture criteria was conducted to verify an approach to predict the fracture load of welds in HSS connections simulated in FE software. Stress-strain (σ-ε) curves of weld and base metals were modelled using tensile coupon (TC) data, a post-ultimate material approximation was validated, and eight fracture criteria were calibrated using experiment results. Twelve large-scale experiments and 158 FE simulations were conducted to investigate the reliability of le formulae in CSA W59:24 for fit-for-purpose PJP-groove welds in CHS X-connections with large branch-to-chord diameter, d1/d0 (= β), -ratios. The results were supplemented with previous FE data to verify the reliability of proposed le formulae. The influence of chord “end effects” was also studied, and design formulae were recommended for welds in connections with 0.10 ≤ β ≤ 1.00.