Dynamic Assessment of Shear Connectors in Composite Bridges with Ambient Vibration Measurements

Shear connectors are normally used in composite bridges, such as slab-on-girder structures, to link the slab and girder together. Damage of shear connectors will result in shear slippage between slab and girder, which significantly reduces the load-carrying capacity of the bridge. Routine visual inspection is not able to detect conditions of shear connectors because they are buried inside the structure. This paper proposes a dynamic damage detection approach based on wavelet packet energy of cross-correlation functions from ambient vibration measurements to identify the damage of shear connectors in slab-on-girder bridges. Measured acceleration responses on the slab and corresponding girder locations under ambient vibrations are used to compute the cross-correlation functions. Wavelet packet decompositions of cross-correlation functions from the undamaged and damaged structures are performed and the percentage of wavelet packet energy in selected frequency bandwidths to the total wavelet packet energy is used to calculate the damage index. Numerical and experimental studies on a composite bridge with a concrete slab supported by two steel girders are conducted to validate the proposed approach and investigate its performance and robustness with noisy measured responses. It is demonstrated that the introduced damage of shear connectors can be identified accurately and efficiently.