Bridge flexural rigidity calculation using measured drive-by deflections

This paper uses simulated deflections on a bridge taken from a model of an instrumented moving vehicle in an attempt to back calculate the distribution of flexural rigidity along the bridge length and hence to evaluate bridge condition. Eight sensors are simulated at different locations on the vehicle. It is assumed that measured deflections are absolute, i.e. they have been corrected for vehicle motion and that the characteristics of the vehicle are known. The unit load theorem is used to relate the measured deflections to the reciprocals of flexural rigidity at every location on the bridge. A Blackman window filter is used to regularise the problem and to improve the conditioning of an ill-conditioned system of equations. In addition, a moving average filter is used to reduce the influence of noise and dynamics, which are sources of inaccuracy in this study. This method is shown to give good results in indicating the presence and intensity of bridge damage and contains some weak information on location.