Stiffness Degradation of FRP Strengthened RC Beams Subjected to Hygrothermal and Aging Attacks

Abstract

The past decade has witnessed an ever increasing interest in strengthening, repairing, retrofitting, andu pgrading of deterioratedco ncrete structures using fiber reinforcedplastics (FRP). Enhancedload carrying capacity by FRP strengthening has been observedby a large number of researchers through experiments at ambient environments. In a harsh environment, however, FRP will degrade. This may result in structural degradation of FRP strengthened concrete members. The possible structural degradation has become a major obstacle for the wide-spread acceptance of this new strengthening technique. In the present study, boiling water and ultraviolet (UV) radiation were used to study the structural degradation of concrete beams strengthened with GFRP and CFRP fabrics. A total of eighteen 170 7.62 15.2 cm steel reinforcedconcrete (RC) beams were prepared as control specimens, conditioned specimens, and unconditioned specimens. Finite element modeling was used to analyze stiffness degradation of FRP layers. The tested and calculated results showed that environmental attacks had a considerable effect on the structural degradation of FRP strengthened concrete beams. 57–76% of the strengthening efficiency and43–48% of the stiffness of FRP were lost after conditioning.