Numerical Analysis of Thermal Behavior of Concrete Cover Around FRP-Bars in Cold Region

Abstract

The coefficient of thermal expansion of fiber reinforced polymer (FRP) in transverse direction is 3–8 times greater than that of hardened concrete. This thermal incompatibility between FRP bar and concrete in transverse direction may cause circumferential cracks within concrete at FRP bar/concrete interface under low temperatures and eventually the debonding of FRP bar from concrete. This paper presents numerical analysis using ADINA finite element software to investigate the thermal behavior of concrete cylinders reinforced with glass FRP bar (GFRP) in cold regions. The non-linear numerical results show that the first circumferential cracks occur within concrete at FRP bar/concrete interface at thermal loads ΔTcr varied between −35 and −25°C for GFRP bar-reinforced concrete cylinders having a ratio of concrete cover thickness to FRP bar diameter (c/db) varied from 0.8 to 3.6 and a concrete tensile strength of 4.1 MPa. The numerical radial tensile stresses in concrete at the interface compared with those predicted from the analytical model are similar until the appearance of the circumferential cracks in concrete whose analytical results are greater. The ratio c/db has no significant effect on the transverse thermal strains at FRP bar/concrete interface and also at external surface of concrete cover for a ratio of c/db ≥ 1.5. Also, the transverse thermal strains, at external surface of concrete cover, predicted from non-linear numerical model are in good agreement with those obtained from the linear analytical model and experimental tests.