Keywords: patch loading, corrugated web, equivalent geometric imperfection.

Corrugated steel plate is a widely used structural element in many fields because of its many favourable properties. This structural layout has spread in the field of bridges, too, especially for steel and composite bridges. Regardless of these numerous applications there are no standard design formulae for the patch loading resistance of girders with trapezoidally corrugated steel webs. The focus of the current paper is the determination of its design value using nonlinear finite element analysis.

Previous experiments, numerical investigations and existing resistance models were studied from the literature. These research activities were focused only on a narrow parameter range of girders with corrugated webs and only a few experiments have been executed, therefore the focus of the current study is the determination of the patch loading resistance using experimental investigation and by nonlinear finite element simulation.

Laboratory experiments were executed at the Budapest University of Technology and Economics, Hungary on twelve simply supported girders. The aim of the experiments is the enlargement of the experimental database for verification of numerical models, and the determination of the patch loading resistance by different geometrical arrangements, loading lengths and loading positions.

Based on the experimental investigations a finite element based design method is developed. A numerical model is built for all test girders and the load carrying capacities are determined by geometrical and material nonlinear analysis including imperfections. Verification of the numerical model is done by the comparison of failure modes, patch loading resistances and load-deflection curves measured in the experiments and calculated in the numerical simulations.

For the finite element based design four equivalent geometric imperfection shapes are analysed. The first critical buckling mode, the ultimate shape and a sine wave imperfection form are studied and a modified sine wave shape is developed which is an approach for the first buckling mode. The aim of the modified sine wave imperfection shape is to give a closed form equivalent geometric imperfection to be applied to the patch loading analysis of corrugated webs.

Imperfection sensitivity analyses are completed for all imperfection shape types and based on the experiments imperfection scaling factors are developed. the calculations showed that the applicable scaling factor is the fold length divided by 200, if the first buckling mode or the modified sine wave shape is used as an equivalent geometric imperfection. In case of the modified sine wave shape imperfection this scaling factor can be applied in all loaded folds and one quarter of it in the two neighbouring folds, while the unloaded folds remain flat. The practically applicable parameter range of the derived imperfections is also determined.

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