A diagnostic survey on the precast prestressed bridge Nižná confirmed significant deterioration due to environmental distress. Evidently, decisive failures of the structure have a similar character as in the previous precast prestressed bridge in Podbiel in the northern part of Slovakia. These failures result from the unsuitable concept of the first generation of precast prestressed concrete beams, which was used in the former Czechoslovakia in the second half of the 20th century. Subsequently, experimental verification using the proof-load test was also executed. This bridge was built in 1956, so at the time of testing, it was 60 years old. The paper presents the indirect determination of prestressing level in one precast post-tensioned concrete beam using the saw-cut method. Experimental measurement was executed during the bridge demolition. Subsequently, a 2D numerical model in ATENA 2D Software, with the assumption of nonlinear material behavior for verification of experimental results, was performed. Finally, the residual prestressing force was evaluated and compared with the expected state of prestressing according to Eurocodes after 60 years of service.
In the early 1950s, the first‐generation of precast prestressed bridges was built in Europe. The prestressing technology was still relatively new and bridges were sometimes executed questionably. The consequences of poor detailing and inadequate maintenance are shown as a practical example of a 59‐years old road precast bridge in Slovakia that recently reached a near collapse state. The behavior of the damaged prestressed precast structure was verified by the full‐scale load test. In the case of advanced corrosion of the tendons, it is often very difficult to accurately determine the actual resistance of a structure. The test results published in the paper may help to find a practical method for the assessment of similar aged existing prestressed bridges.
The first precast post-tensioned bridges in Slovakia are approaching 60 years of their service life. Facing an aging infrastructure, it is necessary to assess their present structural condition and residual life expectancy. Different types and methods of anchorage system were developed and available for first post-tensioned bridges around the world. The reliability and functionality of anchorages contribute to the proper behaviour of post-tensioning system. The considerable effect of aggressive environment (frost, chloride salts, humidity) and environmental load (CO2) leads to corrosion of anchorages and prestressing steel with the risk of a sudden unexpected damage to bridge. The research work deals into finding more details of this structural part. During the demolition of damaged post-tensioned bridges built in 1960s several anchorages were removed and analysed. The material properties, size parameters and performed tensile tests of a wedge anchorage system are summarised in this paper. The findings from this study can be used as input parameters for numerical simulation and durability assessment of similar aged existing post-tensioned bridges.
Reliability is one of the most significant requirements for structures given in Eurocodes. Thus, the specific level of safety, serviceability, and durability have to be satisfied to fulfill the reliability of structures. In the case of reinforced concrete (RC) members, the corrosion of reinforcement is not assumed in the stage of structure design, which is in contrast with the structures in service, where the corrosion of reinforcement can significantly decrease their diameter ø in time. In these cases, the moment resistance in time MRd(t) decreases during the designed lifetime Td of a structure. The corrosion speed is as a basis for the calculation of moment resistance in time MRd(t), i.e., a first-year corrosion rate rcorr and a corrosion model as well. The corrosion itself is a very complicated issue, so the first-year corrosion rate rcorr and also the corrosion model can be different under various conditions in Slovakia. The paper is focused not only to determine the corrosion speed (first-year corrosion rate rcorr and the corrosion model) and parametric study of the moment resistance in time MRd(t) under various conditions in Slovakia but also shows an overview on some parameters that may influence the corrosion process.
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