Evaluation of ultimate buckling strength of stiffened plate for marine structures

In this study, ultimate strength of stiffened plates for marine structure is evaluated by nonlinear numerical analysis technique. Effects of non-dimensionless geometric parameters, material characteristics and fabrication induced imperfections are considered. Results confirm that ultimate strength decreases as the value of plate transverse flexural strength increases with failure mode changing from plate induced overall buckling to plate buckling. Hot rolled plate shows variation in material properties along the thickness direction, this phenomena is incorporated in the numerical simulations and results shows its significance on the buckling strength. Additionally, combine effect of strain hardening and variation in material properties along the thickness direction, yields remarkable increase in ultimate buckling strength of the stiffened plates. Effects of fabrication related imperfection are also evaluated and it is found that imperfections have severe effects on the ultimate buckling strength of stiffened plate. Even at certain value of imperfection stiffened plate buckles prior reaching to its yield strength. It is also found that as the plate flexural slenderness is increasing, imperfection effect becomes more dominant and post buckling response also become sharply unstable. Comparison of numerical analyses results with design guidelines formulated by Detnorske Veritas (DNV) and the American Petroleum Institute (API) is also made. Comparison indicates that, in case of plate induced overall buckling, the guidelines results have good agreement with numerical results.