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 Puente de Alamillo, Seville, SpainThe direct Purpose of a bridge, and the Materials from which a bridge is made, are reasonably easy to read - though the social consequences may not be easy to predict. The form of a bridge is not as easy to read so let's now focus on that. Form is shape, pattern, organisation or manner in which parts are arranged. Two contrasting examples from different centuries - shown in the pictures - are the Alamillo Bridge in Spain and the Sodbachbrucke, a covered bridge in Switzerland. The suitability of a form depends on the purpose of that form. If our purpose is aesthetic then the form is judged as a work of art. If the purpose is to provide a function then the form must be such as to provide that function. Note that fulfilling a functional purpose is necessary but not sufficient for fulfilling an aesthetic purpose.  Sodbachbrucke, SwitzerlandThe form of a bridge has to satisfy many requirements. It must be:- Again note that being technically safe is a necessary but not sufficient requirement. An existing bridge may be cost more than planned, may be ugly, culturally inappropriate and environmentally unfriendly but it cannot be unsafe. It is therefore unsurprising that bridges tend to be classified by technical requirements and that it is difficult to find a simple name for one kind of bridge. We have to think about it in layers - as we do for many other things in life. For example books have layers of form - see next page. |
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