Fatigue of stay cables inside end fittings: high frequencies of wind induced vibrations

A twenty year old stay cable was dismantled because it showed many wire breaks at one of its terminations. The examination of the wire failures showed evidence of fatigue. Analysis of the dynamic behaviour of the stay cable was carried out. It showed that the combination of flexural bending stresses with fretting stresses between the outside layer and wire serving lead to a stress range beyond the endurance threshold. Recorded measurements of transversal vibrational displacements near the sockets show that high modes of wind induced Vibrations (Karman Vortex) were involved in the fatigue occurrence. Examination of the internal state of three other cables confirms the analysis of displacement records in relation with the fatigue limit.

 Author(s): Siegert, D. & Brevet, P.