ABSTRACT

Buckling/collapse analyses of stiffened ship panels under bi-axial thrust loads are carried out and collapse behavior of the panels is investigated. The main purpose of this study is the detailed examination of failure mechanisms of the stiffened panels under combined load cases for developing an approximate method to estimate the ultimate strength of panels. Finite Element Method is employed for the computations. Analysis steps are also provided so that to present a guide for such structural analyses.

At first, only longitudinal thrust loads are considered. Then, bi-axial load cases are simulated. The target panels are adopted from bottom of a bulk carrier. Two different stiffener cross-sections, namely Tee bar and Flat bar are considered. Triple span-triple bay (1/2+1+1/2) modeling extent with periodical boundary conditions is employed. Number of stiffeners is utilized as two and four. The obtained ultimate strength values are compared with those available in the literature and a good agreement is achieved. When the transverse compression is dominant loading, it is observed that the ultimate strength values are relatively higher than those of linear buckling analyses. Influence of the number of stiffeners is considered as small on the buckling strength of the panels, while this effect is negligible on the ultimate strength values. Effects of different loading ratios are examined and it is figured out that the evaluated ultimate strength values for 𝜎_𝑥: 𝜎_𝑦 = 0.2: 1 and 𝜎_𝑥: 𝜎_𝑦 = 1: 0.2 cases are slightly higher than those of the uniaxial transverse and longitudinal thrust cases, respectively. Moreover, for 𝜎_𝑥: 𝜎_𝑦 = 1: 0.2 case, the buckling mode shape has two half-waves in longitudinal direction, which apparently shows necessity of the periodical boundary conditions. In case of dominant transverse compressive thrust, the Von Mises stress distributions suggest that some parts of plate behave as plastic hinges while remaining parts in plating are still in elastic range.