The most typical consequence of hull girder collapse is the breaking of the hull into two parts as a result of extreme vertical bending moment exceeding the ultimate hull girder strength. Therefore, the ultimate strength of ship hull girder should be known even at the earliest stages of ship design process. The purpose of this study is to develop a fast and reliable calculation model in order to determine the ultimate strength of ship hull girders. The paper describes a new iterative numerical approach for strength of stiffened plates, where the cross-sections remain plane assumption is imposed and the deflection curve is determined by using the curvature values directly against solving by differential equations. The deflection curve is taken as the assembly of chains of circular arcs and performed by Smith's method. The hull girder ultimate strength of a VLCC is analyzed using the proposed simplified method based on iterative approach.