Are Reinforced Concrete Girder Bridges More Economical Than Structural Steel Girder Bridges? A South African Perspective

This study investigated the cost-effectiveness of steel girders compared with conventional reinforced concrete girders used in bridge construction in south africa. the investigation considered an existing bridge which required widening as a result of increased traffic flow. the consulting engineers chose two 10 m reinforced concrete girders for the end spans, while two 22 m post-tensioned reinforced concrete girders were used for the central spans. to determine the cost-effectiveness of the consulting engineer’s choice, steel girders were designed for the 10 m and 22m beams based on the relevant south african design codes of practice. the analysis was conducted for both non-composite and composite action between the steel girders and the reinforced concrete bridge deck. based on the design calculations, a cost comparison was performed. the investigation revealed that steel girders are an economically viable option when off-the-shelf steel sections up to 10m in length are considered. for the 10 m girders, a significant cost saving was achieved for both noncomposite and composite construction compared with reinforced concrete. however, for the 22m spans, the post-tensioned reinforced concrete girders are significantly more cost-effective compared with steel plate girders. thus, bridge design engineers should consider steel girders as an option during the conceptual design stage for end spans. a survey was also conducted among senior engineering professionals to determine the reason(s) for the apathy towards using structural steel sections as girders in bridge construction in south africa.