Influence of the Length of Patch Load on the Ultimate Load of Longitudinally Stiffened Plate Girders

An experimental-numerical analysis regarding the ultimate strength of longitudinally stiffened I-girders subjected to concentrated loading is presented. The driving force for this research was to investigate the influence of patch load length on ultimate capacity of longitudinally stiffened girders. In order to assess the patch loading resistance of plate girders, a nonlinear finite element analysis has been performed. The numerical results are compared with the experimental tests using different patch load lengths. For a better verification with the experimental results, the finite element model includes the experimentally measured initial geometrical imperfections and material properties based on the laboratory tests. It has been shown that the numerical and experimental results are in perfect agreement which enabled a fruitful background for parametric analysis, in which different initial geometrical imperfections have been used to ameliorate understandings about their influence on the ultimate load under different patch load lengths. Conclusively it may be stated that initial geometrical imperfections can play a decisive role, especially for stiffened girders. Initial geometrical imperfections of stiffened girders that correspond to deformed shapes at collapse (collapse-affine imperfections), will give the most unfavorable ultimate strengths. In the present paper, the third buckling mode of stiffened girders corresponds to the deformed shape and the lowest ultimate strengths are obtained. Future experimental and numerical work will consider the effects of different geometry, material characteristics and aspect ratio of web plate.

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