Fatigue life assessment of FRP cable for long-span cable-stayed bridge

This study evaluates fatigue life of carbon fiber reinforced polymer (CFRP), basalt fiber reinforced polymer (BFRP) and steel cables considering the sag effect for cable-stayed bridges with various safety factors. The fatigue cycles of the cables during designed service period were first studied by an analysis of vehicle load statistics. The least favorable cables and their stress amplitudes were determined by finite element (FE) analysis. Fatigue life assessment based on the design stress and service life of the cable was conducted by developing the combined algorithm of equivalent transformation. The results indicate that the cables in the bridge undergo approximately up to 1.14 x 10(9) fatigue cycles during 100 service years. The most unfavorable cable is the one in the mid-span position, and its equivalent stress amplitude is almost 12 times the actual stress amplitude. The fatigue life of CFRP cables increases much faster than that of BFRP and steel cables with increasing of safety factor. The fatigue lives of CFRP and BFRP cables are 3 and 1A times, respectively, compared to that of a steel cable with the safety factor of 2.55. To satisfy 100 years of design life, safety factor of CFRP, BFRP and steel cables should be no less than 2.55, 3.27 and 3.64, respectively.