Empirical formulations for estimation of ultimate strength of cracked continuous unstiffened plates used in ship structure under in-plane longitudinal compression

Abstract

Nonlinear finite element method is used to investigate the ultimate strength of cracked continuous unstiffened plates under in-plane longitudinal compression. Various crack length, slenderness and aspect ratios of the plate are selected to assess their influence on the ultimate strength magnitude. Based on the results, an empirical formulation is developed to estimate ultimate compressive strength of the plates. The formulation implicitly includes effects of initial deflection and welding residual stress. A series of finite element analysis are carried out in order to create a data bank based on which regression analysis is used to derive the formulation. Obviously increase in crack length, decreases ultimate strength. It is assumed that ultimate strength varies linearly with change in the crack length. However, results show that rate of change of ultimate strength varies for different slenderness ratios. As the plate becomes more slender, rate of change of ultimate strength gets lower. Based on the results it can be said that ultimate strength of an intact plate plays an important role in estimation of ultimate strength of the cracked one. Additionally except for the crack length and slenderness ratio, it is seen that the behavior of plates with aspect ratio equal to one is different from other aspect ratios. Therefore a set of empirical formulae are also derived for ultimate strength of intact plates based on plate slenderness and aspect ratios. Predictions are then compared to those of finite element analysis and a simple formulation previously suggested by Paik et al. A very good agreement exists between the results and the formulation can be used to predict ultimate strength of cracked plates for wide ranges of crack lengths, slenderness and aspect ratios.