Abstract: Based on the theory of flexiblestiffener, an equalstability level based optimal stiffener design method was proposed for moderately thick plates by taking the uniaxially compressed stiffened panels as objects and utilizing the ultimate strength formulations of weakly stiffened thick panels. During the optimization process, the numbers and geometric sizes of stiffeners are chosen as design variables; the weight ratio of stiffeners to plate is defined as single objective function; a series of restrictions such as stiffened panel collapsing according to the overall buckling mode, stiffeners and plates between stiffeners being avoided from locally buckling, and panel’s ultimate strength meeting the corresponding design requirements are set as constraint functions. Two optimization theories named constrained mixed integer nonlinear programming (CMINLP) and constrained nonlinear programming (CNLP) are adopted, and two optimization tools, MATLAB and YALMIP, are employed. The results of examples show that the equalstability level based optimal stiffener design is safe and feasible for moderately thick plates. The present method gives a more economical stiffener layout than the current rigidstiffener design method on the premise of the same requirement of panel’s ultimate strength, and the stiffener’s consumption is less as the panel’s slenderness ratio is decreased.

Key words: moderately thick plate, stiffener, uniaxial compression, equalstability level, optimization design