The influence of phase changes on the residual strains in a welded hollow steel beam were investigated. A D-section beam is fabricated by U-bending 6 mm thickness SS142712 plate and welding in 10 mm thickness SS142132 plate under restraint at 0.993 MJ/m heat input. Finite element analyses were used to determine residual stresses due to cold bending and for thermomechanical welding analysis. Previously published modelling was modified to include the effect of transformation induced plasticity; cross weld residual strain distribution predicted by the two models and measured experimentally were compared; discrepancies are discussed