For a new safety fatigue design concept of civil engineering cables
Safety fatigue design of civil engineering cables is based, today, on one hand on a maximum stress level and a limitation of stress range in service, and on the other hand on a fatigue test under pulsating tension of a specimen of cable with its anchorages. According, for example, to DIN 1073, the stress range of this fatigue test can be 150 MPa. Fatigue behaviour of civil engineering cables is lass known that the one of mining ropes or cables for aerial rope ways. For those, many studies have been made on the subjects of fatigue behaviour under bending and bending tension. ln civil engineering, this is not the main problem and it is recognized that the most critical points are the anchorages and that breaking of wires will occur, preferably, near of or inside these pieces. Unfortunately there is, it seems, a lack of knowledge on the actual failure mechanisms and only few publications on this subject are available. Due to the evolution of building technologies for large bridges, with the emergence of external prestressing and the development of cables-stayed bridges, it appears necessary to give attention to safety and durability of cables used in such works and to set up a research program "For a new safety fatigue design concept of civil engineering cables" with a cooperation between manufacturers, users, laboratories and academic institutions. The purpose of this research program would be, according to the type of the cable and of its anchorages, depending on the solicitations, to supply the designer with a lifetime bracket and safety margin.
Author: D. Francois J.P. Gourmelon