Ultimate Compressive Strength of Eccentrically Loaded Stiffened Panels in Ship Structures: A Computational Study

Ship scantlings are obtained through a linear elastic design framework. In relatively long ships, the mid-ship’s ultimate strength capacity must be checked whether it is below a certain level (given factor of safety). Smith’s method is based on an incremental-iterative approach where constitutive equations of idealized representative components are used to model the different involved buckling modes. The literature body neglects the local bending effect applied at the stiffener with the attached plating (considered here as the representative element). This work studies the eccentrically loaded representative element from its compressive resistance point of view. The eccentricity sources from the linear varying strain field produced as a result of pure bending of the ship’s mid-section and is relative to the location of the stiffened panel from the ship’s section Neutral Axis. Therefore, the representative element has been considered as a part of the ship’s structure and the inherent eccentricity is analytically calculated in terms of geometric and material properties. A computational study has been further performed in a non-linear finite element environment in order to figure out the effect of the eccentricity level to the ultimate compressive strength of the representative element. Geometric distortions have been also included in the FE models in order to allow for accurate strength calculations. Numerical results have shown that, in realistic proportions of large ships, the further the representative element is located from the mid-ship’s NA the smaller is the deviation from pure compressive load strength analysis results. However, for the element laying near the ship’s NA, idealized models overestimate the strength by 10% compared to realistic analytical / numerical results for the typical scantling case considered.