Title:
Relaxation, Creep, and Fatigue Behavior of Carbon Fiber Reinforced Plastic Tendons
Author(s):
Hamid Saadatmanesh and Fares E. Tannous
Publication:
Materials Journal
Volume:
96
Issue:
2
Appears on pages(s):
143-153
Keywords:
environments; modulus of elascity; Poisson's ratio; prestressing steels; tensile strength
DOI:
10.14359/438
Date:
3/1/1999
Abstract:
Corrosion of steel tendons is a major problem in prestressed and post- tensioned concrete structures. Fiber reinforced plastics (FRPs) are a promising alternative to steel due to their high tensile strength, light weight, and resistance to electrochemical corrosion. Different types of FRP tendons have been developed to potentially replace steel tendons in areas where corrosion is a problem. However, before FRPs as prestressing elements can be used in a field application, their long-term behavior must be investigated. This paper presents relaxation, creep, and tension-tension fatigue test results of two carbon fiber reinforced plastic (CFRP) tendons, namely, Leadline PC-D8 8-mm (5/16-in.) diameter, and 1 x 7 to 7.5-mm (5/16-in.) diameter carbon fiber composite cable (CFCC). Twelve Leadline and 12 CFCC tendon specimens were tested in air at temperatures of -30, 25, and 60 C to determine their relaxation behavior. In addition, the relaxation behavior of 24 Leadline and 24 CFCC samples was examined in chemical solutions simulating aggressive field conditions. The loss of tensile force for the 3000 hr test duration at stress ratios of 0.4 and 0.6 was generally less than 10 percent and it depended primarily on the initial stress level, and the type and temperature of the environment. Preliminary investigation of creep behavior of Leadline and CFCC in air and in chemical solutions was also conducted. Six samples of Leadline and six samples of CFCC were subjected to sustained load at room temperature in air, alkaline, and acidic solutions for a period of 3000 hr. Creep behavior of both tendons was good; however, the creep strains were higher in solutions than in air. Furthermore, 190 samples of Leadline and CFCC were tested in tension- tension fatigue to examine the effect of repeated loading on the elastic modulus, Poisson’s ratio, and the tensile strength of these types of tendons. Fatigue strength was generally good and depended on the stress range and initial stress level.