A Numerical Study on Elastic Buckling and Ultimate Strength of Compressed Trapezoidal Plates

According to Eurocode 3, the design of plated structures may be carried out using three different approaches: effective width method, reduced stress method, and finite element analysis (FEA). For the particular case of elements under compression, the effective width method makes use of the plate buckling slenderness to obtain the corresponding effective cross-sectional area. Since the effective width method was developed for uniform web and flange panels, Eurocode 3, and most design codes, has no specific provisions for the particular case of nonrectangular panels, stating that they may conservatively be treated as rectangular panels with this larger width. With the final objective of improving design rules for tapered members, this paper first presents finite element (FE) numerical results for the elastic buckling coefficient of trapezoidal plates under compression. Four cases are considered which correspond to different boundary conditions usually present in webs and flanges of steel profiles and rectangular hollow sections. Numerical results are used to propose approximate closed-form expressions that can be used to compute local buckling loads for trapezoidal plates in a direct way. Additionally, ultimate strength is obtained for a number of compressed trapezoidal plates using nonlinear geometric and material FEA with equivalent geometric imperfections. Contrary to the philosophy of Eurocode 3, results show that there is no clear correlation between buckling loads and ultimate strength.