Overview
Today pre-stressed concrete bridges represent well over 50 percent of all bridges built. This increase has resulted from advancements in design and analysis procedures and materials, however the life of a concrete structure is still dependant on corrosion of the many internal steel reinforcements. As above, there appears to be a complete lack of appropriate international standards or specific regulations dealing with the Ultrasonic non-destructive testing (NDT) of concrete and reinforced concrete bridge structures. NDT methods for concrete structures consist of Impact hammer echo, ultrasonic velocity, radiography, Quantitative Acoustic Emission (QAE) and Ground Penetrating Radar (GPR). However, they all provide limited information and require a high level of technical interpretation.
Cross-It project will develop a new technology based on Ultrasonic Guided Waves, Automotive thermography and advanced GPR techniques to inspect the concrete structure for dangerous levels of age-related degradation, which could consist of cracks due to water ingress and corrosion of internal steel re-bars and reinforcement.
The developed Guided Waves technology will be able to scan the concrete and display the results as a visual map on a connected laptop. The laptop will run a purpose designed condition monitoring program based on advanced artificial Intelligence like a Neural Networks to match the ultrasonic patterns. Cross-it system could be also permanently installed to the bridge structure to enable a real time structural health monitoring system.
Funding
Results
Technology to better monitor and assess large concrete bridges
Bridges are essential to Europe's transportation infrastructure, yet the ageing reinforced concrete structures are increasingly subject to failure. An EU initiative sought to introduce novel ultrasound technology that detects internal damage for simple and efficient diagnoses.
Concrete is the construction material of choice for bridges, but the majority require reinforcement in the form of steel bars and tendons to increase load-bearing capacity. When cracks develop in the concrete and water seeps in, the water can corrode steel reinforcements. As the loads continue to rise compared to the original specifications, the need for sensitive and accurate non-destructive testing (NDT) methods and structural health monitoring technologies has become more pressing.
The EU-funded http://www.crossit-project.eu/ (CROSS-IT) (Smart condition monitoring and prompt NDT assessment of large concrete bridge structures) project set out to develop novel technology to address this need.
Project partners developed an efficient and cost-effective monitoring technology based on ground-penetrating radar (GPR) to locate internal steel-reinforcing bars. They also developed ultrasonic guided waves (UGWs) to inspect the steel reinforcements of concrete structures.
Researchers modelled UGWs in concrete and tendons and identified optimum propagation modes through the interface among concrete, steel reinforcement and tendons. They selected UGW transducers to propagate the modes determined from modelling and experiments.
The CROSS-IT team developed, tested and validated an integrated system software to automatically detect defects. They advanced software and hardware to combine the GPR and UGW signals in order to display results to the operator.
CROSS-IT's system significantly reduces inspection time compared to existing inspection methods. Further, UGW use allows for a much greater inspection range from one single location than previously achieved. It will also minimise the need for corrective maintenance, leading to a significant decrease in overall operational costs. Project outcomes could one day revolutionise bridge inspection and maintenance procedures, all the while enhancing the safety of EU citizens.