Design is inevitably a team exercise. At its simplest, the bridge designer will have another engineer and one or two draftsmen working directly for him, while on large bridge projects the core team may include ten or more people. Generally, other specialist disciplines will also be involved for part of the design period, such as geotechnical engineers, quantity surveyors and the suppliers of proprietary products such as the bearings, expansion joints etc. An architect may also be involved, either as a partner in the concept or as a specialist involved in the design of finishes, handrails, lighting and other decorative aspects. Depending on the form of contract, some decisions are likely to require input from the client or the contractor.
If the design is to be anything other than banal, the team needs a leader who makes the project his own. There is no aspect of a bridge design that is not capable of more than one solution, whether it is the overall concept or the type of bridge bearing. There is thus great potential for diverging views and for indecision. This multitude of design decisions must be welded into a coherent project, and this can only be done successfully through one mind.
This need for a 'chief designer' is sometimes challenged by professionals, who claim that design is the result of collective decision making, with no one dominating the process. However, it is usually only necessary to consider what the effect on the design would be if each member of the team were to be substituted in turn. For most of the members, the result would be only minor changes to the finished design, while generally there is one team member whose substitution would change the project fundamentally.
In order to carry out his synthesising role, the designer must know enough about all the various specialities involved, so that he can understand the implications on the design as a whole of making one choice or another. Clearly, the designer is not expected to be skilled in all these various disciplines, but he must be able to question the specialists, understand the reasons for their choices, challenge their decisions, take second opinions and ultimately accept responsibility for them. In particular, the bridge designer should have a reasonable knowledge of soil mechanics, as decisions on foundations often determine the type of structure to be built.
This concept of the chief designer and the skills he requires is not new. In Chapter 1 of his first book, Vitruvius discusses the education of architects (which were not differentiated from engineers) in republican Rome, and puts forward the view that very few people can be expert in all the disciplines involved in construction, but that architects must deal with them all, with only imperfect knowledge. He goes on to ask the reader's forgiveness for his imperfect grammar, as he is an architect, not a gifted writer. Perhaps as a civil engineer, I may ask for the same indulgence!
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