Are reinforced concrete girder bridges more economical than structural steel girder bridges : a South African perspective

Abstract EN

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.