Detecting deck damage in concrete box girder bridges using mode shapes constructed from a moving vehicle

Abstract

Longitudinal cracks at the bottom of the deck are a common form of hidden damage in box girder bridges. Timely detection of deck cracking is critical to ensure the safe operation of box girder bridges. This paper proposes a damage detection method for the deck of box girder bridges using mode shapes constructed from a moving vehicle. One stationary excitation vehicle excites the local bending modes of the deck, and the other vehicle moves along the planned path. The moving vehicle acceleration is collected to construct mode shapes on the driving path. First, generalized beam theory is used to analyze the dynamic behavior of the box girder bridge. The theoretical model of the proposed approach is built to analyze the response of the vehicle-bridge system under shaker excitation, and mapping relationship between the instantaneous amplitude of the vehicle response and the local bending mode of the deck is deduced. The damage indicator based on the mode curvature is used to determine the crack position. Then, a damage detection process for field testing is proposed. Technical details such as excitation parameters, driving path, and narrowband filtering are explained. Finally, factors that affect damage detection, including road roughness, crack length, and crack height are investigated via numerical analysis. Results show that the proposed method can detect medium damage.