Fatigue of staying cables Organization and results of the research programme

The fatigue behaviour of the cables is a major factor of safety for cable-stayed bridges. ln order to improve knowledge in this matter, a research programme about fatigue of staying cables was initiated ten years ago. At that time, fatigue design and calculation of Civil Engineering cables was based on the results of tension-tension fatigue tests on cables together with their anchorage on one hand, and on the other hand by setting a maximum stress value and stress range in service. It is still the case today and those conditions are still required in PTI recommendations related to the design, testing and installation of stay-cables. Less was known about the fatigue behaviour of civil engineering cables than those used for mining or ropeways. Several studies had been performed on the latter related to fatigue resistance under bending or tension, which is not the main problem for civil engineering cables. For stay cables, the critical points are at the anchorage and wire breaks could occur nearby or even inside them. However, the damage mechanisms were not fully understood and few papers were available on the subject. The main purpose of the research programme was to provide the designer with data, with a safety margin, concerning the expected lifetime depending on the type of cable, anchorage and foreseen load effects.

 Author(s): Gourmelon, J-P.