Acoustic Emission Monitoring of Concrete Hinge Joint Models

Currently in the United Kingdom there are over 100 bridges containing hinge joint components, introduced to simplify and standardise designs. Visual inspection of hinge joints noted bridge deck waterproofing failure, which can cause steel reinforcement bar corrosion. This reinforcement is crucial to the integrity of the joint, and the loss of reinforcement section can induce higher stresses leading to eventual failure by yielding. The Transport Research Laboratory created a model of two hinge joint assemblies typical of those found in reinforced concrete slab bridges. The model had notched reinforcement bars at the hinges. The aim of this investigation was to determine the effectiveness of the acoustic emission (AE) technique in detecting and locating the cracking of concrete at the throat. AE sensors were attached to the steel reinforcement bars using waveguides and to the concrete face of the model. The model was statically loaded until failure. To allow the visual inspection and logging of concrete cracking around the throat, the load was applied in stages with a brief hold period between each stage. AE results showed that it was possible to identify and locate cracking of the concrete around the throat and that this technique needs to be further evaluated on bridge structures under live loading.