Design Optimization of Composite Steel Box Girder in Flexure

Composite girders consisting of concrete deck on built-up girders are frequently used in bridge construction for their economic advantages. The use of composite girders results in a very economical design. Additional savings can be obtained in design and material costs for some members by automating design approaches based on optimization techniques. This paper describes the use of EXCEL Solver to find the minimum weight for a composite trapezoidal box cross section for a two lane bridge. Design aid tables were generated for structural steel Grades 250, 345, 485, and 690MPa, and different spans varying from 3.0–100m. The search for the minimum cross section used in this research satisfies the 17th Edition of the American Association of State Highway and Transportation Officials Specifications—Load Factor Design method.