Long-Term Behavior of Concrete Beams Prestressed with Carbon Fiber Tendons

Abstract

Much research has been conducted on the short-term behavior of concrete members prestressed with FRP tendons, but relatively little is known about the long-term behavior of these members. This lack of knowledge is one important factor hindering the widespread use of FRP for prestressing. Therefore, a comprehensive study of the long-term response of FRP prestressed concrete members is necessary before FRP can gain acceptance as a viable construction material. This paper describes a part of an on-going test program to investigate the long-term behavior of CFRP prestressed concrete beams. The scope of the program includes eight large-scale T-beams constructed with different levels of prestress. The study considers fully prestressed and partially prestressed sections. For the long-term tests, the specimens are subjected to a sustained loading, higher than the cracking load of the partially prestressed members, maintained constant for several months (about 10,000 hours). The results of the long-term test show similar behavior between beams prestressed with CFRP tendons and that prestressed with steel strands. The ratio of long-term to instantaneous deflection was higher for beams prestressed with CFRP tendons than for the beam prestressed with steel strands. The overall deflection of the CFRP tendons was however smaller than that of the steel prestressed beams.