Medium Span Flat Arch Bridges: Efficient or not?

Abstract

Historically, medium span bridges were generally composed of arch structures made of stones, masonry, and concrete or of metal construction. Despites the inherent efficiency of the form, modern traffic development in combination with the evolution of materials, arches were gradually replaced by frames and girder structures. Now in the UK, the most commonly road and rail bridge solution for medium spans (range between 30 m to 80 m) is the steel-concrete composite deck type with conventional plate girders connected to reinforced concrete deck slabs. This form of construction has dominated the UK construction market for the past 25 years. However, tomorrow construction challenges for our modern societies depends on delivering sustainable designs with consideration for resources efficiency. Arches and shells are “form-active” providing higher degrees of structural efficiency than the girder system. Could this be a new opportunity for arch bridges to become more competitive? This study compares the efficiency of a recently constructed 50 m span flat arch road bridge with a selection of alternatives in forms and in materials. Each option is presented considering the quantities of material, the estimated construction costs, the estimated duration of site works, the whole life cost aspects and consideration for the risk assessment factor. The efficiency ratio of each option is then compared to the flat arch bridge solution.