ABSTRACT
In the broadest sense, failure of a bridge occurs whenever it is unable properly to fulfil its function, i.e. to carry the primary loads across an opening. Some examples may be given.
It may be found that a bridge is unable to carry its full design loads and, for this reason, a load restriction is placed on the bridge. This is, in a sense, a failure. Again, the form of the bridge may be such that, in periods of high wind, traffic is unable to cross. An example may be found in the large suspension bridge built in 1966 to cross the Severn estuary in England (O’Connor 1971a: 380ff). Here, the design incorporates a number of features that were advanced at the time, intended to protect the structure against aerodynamic instability. One of these was the adoption of a streamlined cross-section, with light (but strong) roadway railings made up of tensioned, horizontal wire ropes. Unfortunately, this streamlined form causes traffic on the bridge to be exposed to strong winds and, for this reason, the bridge may be closed to traffic (see Section 12.2). It is not sufficient to protect only the bridge from wind; rather, it is required that the traffic should also receive suitable protection.
