Cases of failure of bridge structures during the process of pre-stressing

Abstract

The paper describes two typical cases of failure of pre-stressing cables during the construction of concrete bridges in Poland. In both cases failure occurred during the tensioning of cables and consisted of the sudden loosening of the cables as well as a destruction of the concrete in the zone under the curvilinear section of a cable. Based on a review of documentation, especially the drawings of zones of failures, and also finite element analysis, it can be concluded that the structure did not have enough reinforcement bars to transfer the tensile forces occurring on the inner curvature of the cables. Therefore, the tensile stresses occurring in these places were only transferred by the concrete. This is contrary to the basic principle of reinforced concrete, which states that tensile forces should be transferred by the reinforcement and compressive forces should be withstood by concrete.