Objectives The aim of this paper is to evaluate the longitudinal ultimate strength of a hull girder more accurately and determine its collapse process.

Methods A bulk carrier is finely modeled in nonlinear finite element software ABAQUS, and the effects of slight, average, and severe welding initial deformations and average welding residual stress on the ultimate strength of the hull girder under hogging and sagging bending moments are fully considered.

Results The calculation results show that the hull girder's ultimate strength and bending stiffness decrease gradually with the increase of the initial deformation amplitude. Severe welding initial deformation makes the ultimate strength of the bulk carrier decrease by 14.25%, and the bulk carrier's ultimate strength decreases by up to 8.22% under the effect of welding residual stress individually. The combined effect of welding initial deformation and residual stress on the hull girder's ultimate strength is not a linear combination of the effects of the two initial deformations individually.

Conclusions The combined effect of welding initial deformation and residual stress on a hull girder's ultimate strength should be considered more carefully in research on the ultimate strength of hull girders.