Compression behavior of GFRP bars under elevated In-Service temperatures

Abstract The use of glass fiber-reinforced polymer (GFRP) bars is becoming accepted as internal longitudinal reinforcement in concrete members subject to compressive load. In building and construction, GFRP reinforcement is subject to elevated in-service temperatures that might soften the polymer matrix and affect the mechanical properties of the reinforcement. That notwithstanding, information on the compressive behavior of GFRP bars under elevated in-service temperatures is limited. This study investigated the effects of elevated in-service temperatures ranging from 23℃ to 140℃ and different slenderness ratios ( L u / d b ) of 4, 8, and 16 on the compressive behavior of GFRP bars. The test results show that the failure mode of GFRP bars changed from fiber-dominant to matrix-dominant with increased temperature. Similarly, the increase in L u / d b ratio changed the failure from shear-crushing to buckling-splitting failure. Furthermore, the GFRP bars retained most of their compressive strength when exposed to temperatures of up to 60℃, but significantly decreased thereafter. The compressive strength retention of the GFRP bars at 140℃ was around 20% regardless of the L u / d b ratio. Based on these results, prediction equations were derived to reliably describe the compressive behavior of GFRP bars and to appropriately determine the minimum concrete cover needed to effectively design GFRP-reinforced concrete members under compression exposed to elevated in-service temperatures.