Application of Idealized Structural Unit Method to Determine the Ultimate Strength of Ship Model in Bending

Abstract The Idealized Structural Unit Method (ISUM) is applied to perform progressive collapse analyses for a 1/3-scaled frigate model in bending. For the load case of pure vertical bending (sagging), the ISUM results are validated against experimental data. The ISUM model is explained in detail taking into account the initial imperfections of stiffeners and the attached plating. In particular, the effect of welding residual stresses on the ultimate hull girder strength is discussed. Displacement controlled nonlinear analyses are performed by using the full Newton-Raphson scheme an incremental iterative solution approach. Furthermore, Smith’s method is applied to determine the progressive collapse behavior the 1/3-scaled frigate model in bending. Smith’s method based calculations are performed under consideration of scantlings and rule based load-end shortening curves of all structural components. Both simplified approaches are applied to determine the progressive collapse behavior of the frigate model in vertical, horizontal and biaxial bending. For the ISUM model the effect of welding residual stress on the ultimate hull girder strength is also proposed for the different load cases.