Evolution and Numerical Prediction of Fatigue-Controlled Regions in Bolted–Welded Joints of Steel Truss Bridges

Abstract

Steel truss bridge nodes are prone to fatigue damage under long-term cyclic loads due to their complex connection forms and significant stress concentrations, which may compromise the service safety of steel bridges. This study develops a three-dimensional nonlinear refined finite element model for typical bolted and welded nodes, considering the effects of bolt pretension, weld toe geometry, and contact nonlinearity, thereby achieving a unified simulation of local node details and overall structural response. By analyzing the stress range, frequency, and evolution of key detail components, the fatigue-critical regions and governing mechanisms of both bolted and welded nodes are identified, and the contribution of each component along complex stress paths is clarified. Based on these findings, a fatigue life prediction method applicable to both bolted and welded nodes is proposed, which effectively reflects the actual stress characteristics and fatigue damage evolution of the nodes. The results provide theoretical guidance and technical reference for fatigue safety assessment and durability design of steel truss bridges.