Dynamic Characterization of a Truss Bridge by Falling Weight Deflectometer
Transportation Research Record: Journal of the Transportation Research Board
Volume 2331 / Structures December 2013 Volume 1
E.V. Fernstrom, J.L. Carreiro, J.D. Rawn and K.A. Grimmelsman
There are several full-scale testing methods that can be used to characterize and evaluate the global performance and condition of bridges. These global methods mainly consist of static load tests and dynamic testing methods using either controlled or uncontrolled dynamic excitation. Each approach has advantages and disadvantages with respect to experimental and logistical considerations, data analysis requirements, and the scope and utility of the characterization results obtained. This paper presents a global dynamic characterization program based on controlled impact dynamic testing that was applied to a truss bridge. The impact testing was performed using a hand-held impact hammer and a falling weight deflectometer (FWD) as dynamic excitation sources. The objective of the project was to evaluate if the FWD, which can produce a broadband dynamic force, can be effectively used as a tool for quantitatively characterizing the performance and condition of bridges. Many transportation agencies already use FWD devices for their pavement evaluation programs and it follows that if the device is suitable for impact dynamic testing of bridges, these agencies could also use their FWDs to quantitatively evaluate their bridges. The paper discusses different dynamic testing approaches and presents an impact dynamic testing program executed for the truss bridge. The results obtained using the two dynamic excitation devices are presented and compared with each other, and with the results from an analytical model of the bridge. Finally, several observations and conclusions related to the efficacy of FWD devices for impact dynamic testing of bridges are presented and discussed.