Author: Oliver, Alistair
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Many bridges constructed on Britain's transportation network are standardised, effectively off the shelf beam or truss designs. Whilst highly economical and practical, these bridges often lack visual merit or interest. Experience in the design and construction of the Tangmere Footbridge has revealed that for a small increase in overall budget, in this case 7% above a basic warren truss, a bridge can be transformed into a unique, interesting and characterful structure. One way of achieving this is with the use of architectural features. This approach however impinges on the controversial question of 'structural honesty' in regard to bridge aesthetics.
The paper explores several examples of structural dishonesty, as well as the logic and basis for the concept. Also discussed are the different emphases placed on design by engineers and architects, especially in relation to the visual impact of infrastructure on society. The paper concludes with a reflection on current practice regarding aesthetic bridge design, and makes some suggestions for developing and honing the skills of bridge designers.
Alistair Oliver, BEng (Hons), MSc, CEng, MICEMott MacDonald
Stress ribbon bridges are an elegant form of construction found in various countries around the world. They use the theory of a catenary transmitting loads via tension in the deck to abutments which are anchored to the ground. The basic and most commonly found form consists of a precast concrete deck with steel tendons. This concept was first introduced by German engineer Ulrich Finsterwalder (1897-1988). Stress ribbon bridges are quick and convenient to construct given appropriate conditions. They can be built with minimal impact to the surroundings and their slender form ensures a visually pleasing end result. A wide range of structures exist in Europe, USA and Japan, including multispan bridges, three way spans and long spans up to 150m built in urban, rural and mountainous areas. The Pai Lin Li Travel Award 2008 was awarded by the Educational Trust of the Institution to spend up to 6 weeks abroad researching worldwide practices in the design and construction of stress ribbon bridges. Meetings were arranged with design engineers and researchers involved in this field in Germany, Czech Republic and Japan over a 4-week period. This paper summarises the results of this research and discusses reasons why this form is not currently popular in the UK. Roma Agrawal , MA (Oxon), MSc, DIC WSP Cantor Seinuk