Efficiency, Originality, and Shaping: Considerations for the Design of Good Bridges

This article examines three important aspects of bridge design that can provide guidance to engineers who wish to design bridges that embody efficiency, economy, and elegance, the three ideals of structural engineering defined by David P. Billington. These aspects are (1) the relation between efficiency and economy, (2) the significance of originality, and (3) the challenge of shaping structural components. Efficiency and economy can only co-exist in a given structure when the ratio of the cost of materials is high relative to the cost of labour. Currently, this is not the case. The importance of originality relates to the visual expression of creative decisions made in design. For bridges, creative decisions made on the basis of purely practical considerations can be a valid source of aesthetic significance. The scope of creativity is not limited to the structural system itself, but rather encompasses the combined entity consisting of structure and site. It is possible to shape structural components on the basis of aesthetic considerations while maintaining a strict discipline of economy. The primary opportunities for using this source of aesthetic significance are created by structural dimensions for which a change produces only minimal effect on structural behaviour and cost.