Recommendations on imperfections in the design of plated structural elements of bridges

• Patch loading in plated beams is very sensitive to initial imperfections.
• It is not necessary to use initial residual stress in the FEM stress patterns.
• We conclude more accurate results than the recommendations of Eurocode 3.
• It is acceptable to adopt initial equivalent geometric imperfections.

High-yield strength steel-plated structures represent competitive solutions when used in steel and steel–concrete composite bridges. Nevertheless, further modifications may still be introduced at the design stage in the case of slender sections, in order to minimize the number of their stiffeners and thereby economize on manufacturing costs. Eurocode 3 “Design of steel structures” specifies design methodologies for slender plates subjected to compression and for stiffeners. Moreover, the use of Finite Element Method (FEM) software is fast becoming an alternative analytical method for the design of complete structures or structural elements, as it offers a more realistic approach. This paper makes recommendations for FEM assessments of plated sections in bridges that take the initial imperfections, geometric imperfections and residual stresses of the sections into account, in order to arrive at realistic results.