Numerical Investigation of Stress Intensity and Geometry Correction Factors in Welded Longitudinal Stiffener Details

ABSTRACT The safe operation of aging steel railway bridges requires reliable fatigue assessment of welded structural details. Welded longitudinal stiffeners, while not directly loaded, influence structural stiffness and are susceptible to fatigue cracking at weld transitions. This study improves the fracture‐mechanics assessment of these details by developing accurate engineering formulas for the geometry correction factor M k . A series of 819 three‐dimensional finite element simulations was conducted using ANSYS, covering 117 geometric configurations defined by base plate width, stiffener dimensions, and weld size. The results show that increasing stiffener height, length, and thickness generally raises M k , while narrower base plates and optimized weld sizes reduce it. A mixed multiplicative–additive regression model was calibrated to the simulation data, yielding closed‐form expressions for M k at both the surface and deepest crack points with high accuracy ( R 2 = 0.942 and 0.979). This work refines earlier approximations and supports practical fatigue assessment of welded bridge details.