Dynamic assessment of shear connectors in slab-girder bridges

Shear connectors are of primary importance in slab-girder bridges to provide composite action. Their damage will reduce the load-carrying capacity of the structure. To test the suitability and efficiency of various vibration-based damage identification methods to assess the integrity of the shear connectors, a 1:3 scaled bridge model was constructed in the laboratory. Some removable anchors were specially designed and fabricated to link the beams and slab that were cast separately. Each anchor consists of a threaded bar that penetrates through the soffit of the beam and ties up into an embedded nut cap to simulate a shear connector in real bridges. Different damage scenarios were introduced by pulling out some connectors. Vibration tests were carried out in each damage scenario. Various damage detection methods have been applied and results show that a local approach was able to detect all the damage successfully and consistently. This new method does not need any reference data for the structure, and therefore it is suitable for application to the prototype bridges. The proposed local method was also compared with some global methods, including optimal model updating techniques. The sensitivity region of this local vibration method for damage detection is also investigated.