Residual stresses in high strength steel welded box sections

Induced residual tensile and compressive stresses generated by the fabrication process can cause premature buckling and reduce the ultimate axial strength of welded steel box sections subjected to compressive loads. Previous research pertaining to induced residual stresses has been restricted to box sections fabricated from mild steel and 460 MPa high strength steel (HSS) using single pass welds or lightly welded sections. To date, very limited research has been undertaken to investigate the residual stresses in box sections fabricated from 690 MPa HSS plates. This paper investigates the induced residual stress distributions in square welded sections fabricated from 690 MPa HSS plates with single and multiple weld passes. The non-destructive neutron diffraction technique has been used to investigate the residual stresses in six test specimens: four specimens fabricated from 5 mm HSS plates using single weld passes, and the other two specimens fabricated from 16 mm HSS plates using six weld passes. Experimental results suggest that the 16 mm thick heavily welded sections exhibited higher tensile residual stresses than the 5 mm thick lightly welded sections, while the compressive residual stresses of the heavily welded sections were similar to the compressive residual stresses of the lightly welded sections. Considering the experimental results, a relationship between compressive residual stresses and width to thickness ratio of the specimens is formulated. In addition, a residual stress distribution model is proposed for lightly and heavily welded box sections.