The welding residual stress in an orthotopic steel deck is investigated through experimental measurements and finite-element simulations. The simulated residual stress fields are in reasonable agreement with the measured results. The weight function method are used to investigate the stress intensity factors (SIFs) at the surface and deepest points of the semi-elliptical surface cracks, subjected to a combination of external load and through-thickness welding residual stress. Different crack aspect ratios and relative depths are analyzed. The results reveal that the transverse residual stress is always tensile through the plate thickness at the middle section, which makes the SIFs of the surface and deepest points larger than those without considering the residual stress. However, the non-linear reduction for transverse residual stress through the thickness causes the SIFs to decrease for aspect ratios of 0.4, 0.6 and 1.0.