Damage identification of shear connectors with wavelet packet energy: Laboratory test study

Shear connectors are widely used to link the slab and girders together in slab-on-girder structures. Assessment of the integrity of shear connectors is an important issue in the maintenance and health monitoring of such structures. In this study, a 1:3 scaled bridge model was constructed with removable anchors linking the slab and girders as shear connectors. Each anchor consisted of a threaded bar penetrating through the soffit of a girder and anchored in the slab by an embedded nut cap with welded steel bar. Different damage scenarios were simulated by removing some of these connectors. A signal-based damage detection method in which the damage feature is characterized by the wavelet packet energy changes was applied to the damage identification of the shear connectors. Using measurements of hammer impact responses, the locations of the loosening of the shear connectors were effectively detected. This paper demonstrates that the wavelet packet-based energy index is a sensitive local damage indicator. The results also show that comparison of the relative vibration between the slab and the girders is a more effective technique for evaluating the shear connector damage than comparison of the vibration of the slab before and after shear connector damage. This finding is particularly interesting because data from the intact (undamaged) bridge is not required. The suitability and efficiency of the approach is expected to be applied in situ to assess the integrity of shear connectors in existing structures.