Numerical Simulation of Weld Induced Residual Stresses in Welded Steel Moment Connections

Abstract This paper presents a comprehensive numerical investigation into the influence of welding sequence on the seismic performance of welded steel moment connections (WSMCs), which are critical elements in steel building frames designed to resist lateral loads. Despite improvements made in WSMC detailing after the 1994 Northridge Earthquake, recent studies have shown that low-cycle fatigue failures still initiate at the weld toe and access hole, highlighting the need to better understand residual stress effects. While it is commonly believed that residual stresses relax during cyclic seismic loading, experimental evidence suggests persistent strain accumulation at critical regions. To address this gap, a detailed three-dimensional finite element (FE) modeling framework is developed in ANSYS, incorporating a sequentially coupled thermo-mechanical analysis to simulate realistic weld-induced temperature histories and resulting multiaxial residual stress distributions. Two WSMC specimens (MC1 and MC2), featuring different welding sequences for the bottom beam flange, are analyzed. Simulation results are validated using experimentally recorded temperature and strain data. The findings demonstrate that welding sequence plays a decisive role in altering residual stress magnitudes and their spatial distribution, especially at the weld toe and weld access hole. These stresses are shown to significantly influence localized strain ratcheting and fatigue crack initiation. Notably, although longitudinal residual stresses relax with inelastic cycles, the multiaxial stress state sustains high von-Mises stresses, which drive continued strain accumulation. This study highlights the necessity of incorporating welding residual stresses and sequence effects into seismic performance assessments of WSMCs to enhance prediction accuracy and structural resilience.