Mechanical performance evolution and life prediction of prestressed CFRP plate exposed to hygrothermal and freeze-thaw environments

The long-term prestressed loss of anchorage system and mechanical property evolution play the significant role for the steel/concrete structures strengthened with prestressed CFRP plates. In the present study, a wedgeextrusion bond anchorage system was applied to provide the reliable anchorage load-bearing capacity for CFRP plate. A new prestressed tension device was put forward to realize the coupling exposure of elevated temperature (20 degrees C, 60 degrees C and -20 to 30 degrees C), distilled water and sustained loading (20%, 40% and 60%). The mechanical and thermal properties of CFRP plate were conducted to obtain the long-term evolution exposed to the above environments. The mechanical analysis and tensile tests of anchorage system showed the tensile failure modes under the static and cyclic loads were the CFRP burst, and there was no debonding occurring in the anchor. The higher anchorage capacity was attributed to the uniform stress distribution of CFRP plate parallel to the greatest dimension of cross section in the anchor. The new prestressed tension device can realize the maximum prestressed level (-70%) with an allowable prestressed loss (-300 mu epsilon). Meanwhile, the prestressed loss of CFRP plate exposed at the maximum temperature (60 degrees C) and longest time (90 days) was found to be -300 mu epsilon. Immersed at higher temperature and prestressed level brought about an additional degradation rate of tensile strength (5%-10%). The minimum strength retention of CFRP plate was found at the freeze-thaw exposure for 90 days. The long-term life prediction showed the residual tensile strength retentions of CFRP plates were more than 50% for the maximum prestressed level (60%) for the service life of 30 years in civil engineering structures.