Cyclic tensile tests on prestressing strands embedded in concrete

The fatigue life of prestressed concrete beams, subjected to cyclic bending, mainly depends on the fatigue behaviour of the embedded prestressing strands. An evaluation of international fatigue test results revealed a reduced fatigue life of embedded strands in prestressed concrete beams compared to single strands in air. The reduced fatigue life can be explained by specific influences and fatigue processes caused by the built-in conditions of strands. Due to the lack of basic understanding, systematic investigations are currently carried out to identify, quantify and describe different influencing parameters and fatigue processes as well as to better understand and determine the fatigue behaviour of strands in pre-tensioned concrete beams. In this article, the experimental investigations regarding the fatigue life of strands embedded in concrete are presented. Within cyclic uniaxial tensile tests on strands in air and strands embedded in concrete, the influence of fretting fatigue processes and friction stresses between the outer wires of strands and the surrounding concrete was determined.