Abstract: A simplified method has been developed in order to analyze the ultimate strength of ship plating under bi-axial compressions . The effects of welding residual deformations and residual stresses are studied . According to the measurements, a tolerance formula of welding reaidual deformations is put forward, The results presented are compared with those of non-linear elastoplastic FEM and experiments . In addition, the effects of corrosions on the ultimate strength of ship plating are discussed