State-of-the-art review of dynamic impact factors of highway bridges

Dynamic impact of moving vehicles on bridges is an important and long-standing issue in the design and evaluation of bridges and has received much attention from researchers and engineers. The use of the dynamic impact factor (IM) to account for the impact effect of vehicles has been widely accepted in bridge engineering. Accurate evaluation of the IM will lead to safe and economical designs of new bridges and provide valuable information for condition assessment and management of existing bridges. Nevertheless, agreement on the evaluation of IMs is yet to be reached. Numerous studies have shown that the evaluation of the IM is a difficult task because it is influenced by a large number of parameters and uncertainties. As a result, different forms and values of IMs are specified by different bridge design codes and this disagreement has been debated in many studies in the past few decades. Furthermore, some field tests observed that the IMs in design codes are overestimated while many other field tests have suggested that code provisions may lead to underestimation of IMs, indicating the need to develop a more accurate assessment method for IMs. It is the objective of this paper to review and summarize the important methodologies and findings of the study of the dynamic IM of highway bridges conducted over the past two decades. While reviewing the advances achieved in the past two decades, much effort was made to identify the remaining controversies and gaps left in this field. Therefore, it is hoped that this review can also provide necessary background information for researchers and engineers to further examine these problems and help identify future research directions in this field.