Numerical Assessment of the Influence of Welding Sequence on the Seismic Performance of Welded Steel Moment Connections

Abstract Seismic experiments on welded steel moment connections (WSMCs) demonstrated that the welding sequence can influence the failure responses by influencing the localized low-cycle fatigue responses. It is widely known that welding residual stresses relax with a few inelastic loading cycles, and hence, there is a notion that the welding sequence or resulting residual stress does not influence the seismic response of WSMCs. Because of this notion, investigations on the influence of weld sequence on WSMC failure responses have been limited. This study developed a numerical scheme based on a sequentially uncoupled thermomechanical analysis technique to simulate the weld-induced residual stress and its influence on the WSMC seismic responses. The simulation technique is validated against the recorded temperatures and strains. The simulations indicate that high residual stresses tend to concentrate near the weld toe and around the weld access holes. Subsequent seismic loading prescribed to the WSMCs in the presence of weld residual stress simulates the influence of residual stress on the localized strain responses. Strain accumulations are simulated at locations where cracks were observed in the seismic experiments of WSMCs. The numerical results also demonstrate the influence of weld sequences on the local strain responses of WSMCs. Finally, the residual stresses at critical locations are found to relax with a few inelastic loading cycles, as widely known; however, strain accumulation persisted with inelastic loading cycles at the locations where cracks were observed in the experiments. The reason for this phenomenon is demonstrated to be related to the influence of the multiaxial stress state at these locations.