Dynamic-Based Assessment of Shear Connectors in Composite Bridges with Data Taken from the Surface of the Deck Slab

Most bridge management systems generally rely on visual inspections for condition assessment; this means that damage in inaccessible parts of the structure, such as shear connectors in concrete composite bridges, can remain undetected until failure occurs. Localised non-destructive techniques are limited to small areas, time-consuming, and require prior knowledge of the damaged zone. These limitations can be overcome by using dynamic-based techniques. This study aims to investigate experimentally the efficiency of dynamic-based techniques in assessing the condition of shear connectors based on measurements taken from the surface of the deck slab. The study involved the construction of five composite beam models, each with a different number of shear connectors. Anchors of 8 mm bars were used to simulate shear connectors in real bridges. Damage was introduced by accelerating corrosion to a group of shear connectors near the supports in each beam model. A dynamic test was conducted on undamaged and damaged beams. Unlike the change in damping ratio, which exhibited inconsistent results, the change in frequency response function, natural frequency, and mode shape showed high sensitivity in detecting the degree of composite action and the existence of damage. In an attempt to locate regions with damaged shear connectors, the change of flexibility method showed minimal negative results compared to other methods. Overall, results show that dynamic-based techniques can be used to detect and localise regions with damaged shear connectors in precast prestressed beams - cast in-situ slab composite bridges by only taking vibration measurements from the surface of the accessible deck slab.