Condition Assessment of a 45-year-old Prestressed Concrete Bridge Using NDT and Verification of the Results

A relatively new field of application for non-destructive testing in civil-engineering (NDT-CE) is damage analysis in the process of regular bridge inspection. NDT-CE methods will be applied for an in-depth investigation if the cause or the extent of damage is not clear. This might be the case for cracked prestressed steel in tendon ducts and its effect on stability. Therefore the reliability has to be proven. In this paper the condition assessment of a 45-year old prestressed concrete bridge with cracked prestressed steel, pitting corrosion and delaminations in the bridge deck will be presented. This bridge was later demolished so that verification of the results became possible. Typical damage pattern especially for delamination in the bridge deck will be presented. For fracture detection of tendon ducts in the bridge deck the combined magnetization and tractor appliance from TU Berlin ready for testing up to 4.000m² in one night shift was applied. The reliability of this method based on Magnetic Flux Leakage (MFL) has been quantified by excavating the tendon duct and determining the POD (Probability of Detection). Additionally combined automated testing with so called “on-site scanning systems” was carried out. Results gained from ultrasonic-echo and radar testing are combined for reconstruction of the inner structure and location of injection faults. The 3-D imaging of the results may help to reconstruct lost as-build-plans and serve for static calculations of “unknown” structures.

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