This paper presents an optimum design of longitudinal stiffeners for box-girder compression flanges. The buckling behavior of longitudinally stiffened compression flanges has drawn considerable interest from early pioneers of theoretical mechanics, as illustrated by Timoshenko and Gere and Bleich. The longitudinally stiffened compression plate structural members generally render an economical structure by efficiently proportioning the material to resist the induced compressive stresses. This study presents results that are based on 3D finite-element analysis of several hundred hypothetical compression flange models stiffened by varying numbers of longitudinal stiffeners with realistic dimensions. The thickness of the compression flange t was varied from 0.50 to 2.50 in. (from 12.7 to 63.5 mm), the number of longitudinal stiffeners n was varied from 1 to 4, and the aspect ratio of the plate panel a was varied from 1 to 5. Two different plate transverse slenderness ratios w/t were analyzed. Analytical data were reduced using nonlinear regression analysis to a simplified design equation suitable for practicing engineers. Several example problems are given to illustrate the use of the regression equation. Comparative analyses are also made to demonstrate the versatility and reliability of the analytical study conducted.
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