Analysis and Optimal Design of Segmental Precast Concrete Bridges with Balanced Cantilever Construction (Case Study: Esteghlal Bridge in Isfahan)

Abstract

The construction of segmental precast concrete bridges is an increase due to its superior performance and economic advantages. This type of bridge is appropriate for spans within 50 to 250 m, known as mega-projects and the design optimization would lead to considerable economic benefits. In this study, a box-girder cross section of bridge superstructure with balanced cantilever construction method is assessed. The depth of cross section, thickness of top and bottom flange, thickness of webs and the count of strands of pre-stressed steel are considered as design variables. The optimum design is characterized by geometry, serviceability, ductility, and ultimate limit states specified by the American Association of State Highway and Transportation Officials (AASHTO) standard and AASHTO Load and Resistance Factor Design (LRFD) specifications. Genetic algorithm (GA) is applied for cost and weight optimization. To validate functionality of this algorithm, a real bridge constructed in the city of Isfahan, Iran (Esteghlal Bridge, completed in 2017) is optimized as a case study. The total of a 13% reduction in cost and weight of the bridge superstructure is observed. The cost optimization algorithm is run by considering different spans and relation between superstructure cost and span length is assessed. The efficiency of applying the GA in optimization of this kind of bridges is proved.

Keywords

• optimization
• segmental concrete bridge
• box girder
• balanced cantilever
• genetic algorithm