A review is presented of the recent technical literature in the English language dealing with bridge dynamics in general and dynamic testing of highway bridges in particular. It is shown that several definitions have been used for the impact factor and thus the same set of field test data may lead to widely varying estimates of the impact factor. In nearly all the reviewed references, there is little or no justification for using a particular definition, suggesting that each of the various definitions was regarded as axiomatic, requiring no justification. It is also shown that there are additional factors that may be responsible for misleading conclusions from the test data; these factors include vehicle type, vehicle weight, transverse position of the vehicle with respect to the reference point, differences in dynamic increment of strains and deflections, presence of bearing restraint forces, and roughness of the riding surface. A preferred method of interpreting the field test data for obtaining a representative value of the impact factor is suggested. It is shown that the impact factor is not a tangible entity susceptible to deterministic validation.
Abstract