Buckling Strength Analysis Of Stiffened Panels Of Ship Structures Using Non-linear FEM

Stiffened panels are the basic strength members in plated structures of steel or aluminumalloys. Ships and offshore structures are built up of stiffened panels. Stiffened plate and shellcomponents have been used for many years in a variety of engineering structures. In navalarchitecture they are used in the construction of ship hulls, while in aerospace industry, theyare used in the construction of aircraft fuselage and wings. The buckling strength of stiffenedpanel is vital for the overall strength of the structure.Buckling and the ultimate strength of ship structures have been widely investigated overthe years by employing analytical methods, experimental tests, empirical approaches and non-linear finite element (FE) simulations.Analytical methods employ first principles and are more mathematically sound, and anumber of studies were carried out by many researchers. Due to the complexity of the issue,analytical methods deal mainly with simplified cases.Nonlinear finite element analysis (FEM) of stiffened panels was not considered practicalfor design purposes due to the cost of modeling and computing. During the last decade due toincrease in computational power this technique has gained popularity. Non-linear FEA isimportant because it can provide detailed structural behavior under specific loading conditionsbeyond the elastic limit.Aim of the present research work is to perform nonlinear Buckling Analysis of Stiffenedplate and panel structures using popular FEA software ANSYS and compare the results of theanalysis with the Analytical methods and Linear Buckling analysis results.For the purpose of analytical calculations two methods were adopted which includedcalculation based on theory of structural strength analysis and design rules by shipclassification societies like ABS, CSR, etc.Nonlinear Buckling analysis was performed using ANSYS software. Model generationand the whole analysis process were completed by using ANSYS Parametric DesignLanguage (APDL). The power of this method is that it provides greater flexibility in themodel generation and analysis process. Furthermore it results in greater time saving whenmany design iterations are needed which require changes in parameters of the model.Different load scenarios were analyzed and finally results were compared with analyticalresults and FE analysis performed by other renowned researchers, to check the accuracy ofAnalysis performed. The whole process has proved that nonlinear FEA is very important toknow Buckling behavior of structures under different loading conditions.Additionally an element was developed to serve as an initial step towards the emergingsemi-analytical FEM technique known as ISUM. For that purpose a code based on theory ofISUM was written in MATLAB for an element which can perform geometrically nonlinearanalysis of plate panels.