ABSTRACT
Values of Rs may be derived from analysis of the types and weights of vehicle which use the bridge, as indicated above. However, derivation of the appropriate DAF is then necessary.
8.3 DETERMINATION OF STRUCTURAL RESPONSE
In theory, bridge response cannot be separated from the vehicle loading (the action), since the movement of a real bridge affects the wheel loads that initiate the original response. Therefore an iterative analysis is required at each time step to ensure compatibility between the suspension and bridge deflections and interacting forces. A number of theoretical studies have been performed for road vehicles and rail vehicles (AEA Technology (Bailey, 1996; Green eta/., 1995)) in which multi degree of freedom vehicle models have been used in conjunction with theoretical road surface profiles and elastic bridge models in order to model the interactions between bridges and vehicles, and thus to obtain the bridge responses. These methods appear to be most useful in very specific applications, for example:
• when refining the design of vehicle suspensions (where the vehicle models are under the direct control of the analyst);
• in military bridging design (where vertical deflections can easily be three or four times larger than the suspension travel of a typical vehicle).
