| FRP cables have been used as reinforcement of concrete structures and structural tension members. Although tensile load relaxation is usually verified by stress relaxation tests for 1,000hours in a laboratory, demonstrative data for long term behavior of FRP cables have not been sufficiently provided. Residual strength after long-term servicing has not been validated sufficiently, and more empirical studies are required. The authors have carried out outdoor exposure tests for 17 years to verify the long-term durability. FRP cables, carbon, aramid, glass, and vinylon fibers, were exposed in various conditions, such as initial prestressing tensile load, with/without direct sunlight radiation. After 3.5, 15, 17 years exposure, the specimens were retrieved and investigated with residual prestressing tensile load, strength, and material degradation. The results suggest that practical durability of carbon and aramid FRP cables seems to be still good, but initial loading level should be carefully considered for glass and vinylon FRP cables. The cables were also evaluated with chemical analysis such as SEM and FT-IR microscopy. Loss of surface resin was observed for all the tested FRP cables; however, the deterioration between fiber and matrix resin was not found. Observation with FT-IR microscopy detected the deterioration in the surface of AFRP cables, and the feasibility of this method of deterioration evaluation for FRP cables was indicated. |
