Buckling and ultimate strength of plates with openings

Openings can be seen on almost every main supporting member of all types of ships. These openings are mainly used for inspection and may be fitted for passing pipes or reducing steel weight. There has been a need for refined strength criteria with which scantlings of main supporting members in the way of and around openings can be more rationally determined. A plate with an opening behaves in a very complex manner when subjected to compressive or shear stress. The mechanisms that can possibly take place are yielding, buckling, stress concentration and cracking. To better understand the complex behaviour, a total of 954 linear and non-linear FEM (finite element method) analyses were performed. Both buckling strength (eigenvalues) and ultimate strength were calculated. Plate panels were analysed as the idealised structural model of main supporting members with openings. Parametric studies were conducted and the investigated variables were slenderness ratio and aspect ratio of panels, shape and dimensions of openings, longitudinal and transverse compressive stresses and shear stress. Simplified formulae were proposed based on the FEM results. Strength reduction factors were introduced to present the reduced buckling and ultimate strengths of plate panels with openings as ratios of those without openings. These simple mathematical functions can be incorporated in a design guidance and can help to estimate the strength of plates on main supporting members in the way of openings.