Fatigue performance of Q370qE steel non-coplanar butt-welded joints with inclined principal stress
Year: 2026
Type: article
Abstract: This study investigates the fatigue performance of non-coplanar butt-welded (NCBW) joints subjected to inclined principal stresses in the cable–girder anchorage zone of cable-stayed bridges through experimental and finite element analyses. Hot spot stresses were measured for NCBW joints with dihedral angles γ ranging from 0° to 8° and angles α between the principal stress direction and the weld axis ranging from 30° to 70°, while crack initiation and propagation were systematically tracked. The results show that stress concentrations occur at the weld toes on the concave side of the non-coplanar joints, with the maximum stress concentration factor increasing with both γ and α and reaching 1.75. Between one and ten cracks initiated in individual specimens, and all cracks propagated approximately perpendicular to the principal stress direction. Three-dimensional scanning and finite element analyses of the weld ripple morphology reveal that pronounced stress concentrations develop at the inter-ripple grooves when they are oriented perpendicular to the principal stress direction. The inter-ripple grooves and adjacent weld toes form elongated notch regions that strongly promote crack initiation. A stress-intensity-factor-like parameter is proposed to evaluate crack initiation locations in NCBW joints subjected to inclined principal stresses. This parameter provides 17% greater explanatory capability for the experimentally observed crack initiation behavior than the conventional hot spot stress criterion. The nominal stress S-N curves specified in current design standards do not provide conservative fatigue life estimates for all specimens tested in this study, whereas the standard hot spot stress S-N curve and master S-N curve family provide conservative estimates for all specimens. Finally, dedicated S-N curves are established for 16-mm-thick NCBW joints subjected to inclined principal stresses at a stress ratio of 0.1. The corresponding design fatigue strengths are 62.5 MPa, 119 MPa, and 185 MPa in terms of nominal stress, hot spot stress, and equivalent structural stress, respectively.
Authors: Junming Zhao, Lin Xiao, Xing Wei, Yingliang Wang
Institutions: Southwest Jiaotong University, China Railway Group (China)
Language: English
Subfield: Mechanics of Materials
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,540
Funder: Southwest Jiaotong University
OpenAlex ID: W7222736391