Bond-Dependent Coefficient of Deformed Glass Fiber-Reinforced Polymer (GFRP) Reinforcing Bars

摘要

Concrete members reinforced with glass fiber-reinforced polymer (GFRP) bars exhibit large crack widths and deflections in comparison with that reinforced with steel bars due to the low modulus of elasticity of GFRP bars. Consequently, the design of GFRP-reinforced concrete (GFRP-RC) members is often governed by serviceability (deflection and cracking) rather than ultimate state. The calculation of the crack width, however, includes an important parameter to account for the bond between the FRP bars and the surrounding concrete which is the bond-dependent coefficient (k_b). This paper presents the test results of an investigation conducted to evaluate the bond bond-dependent coefficient (k_b) of newly developed helically-deformed GFRP bar. A total of 4 concrete beams (200×300×3100 mm) were constructed and tested in four-point bending in accordance with the new test method presented in Annex S of CSA S806-12 "Test Method for Determining the Bond-Dependent Coefficient of FRP Rods". The investigation included four different diameters of the deformed GFRP bars, namely: 12, 16, 20, and 25 mm. The predicted k_b values were compared with the recommendation of ACI 440.1 R-06 design guidelines and the CSA S6-06 Code. The average k_b value of the newly developed helically-deformed GFRP bars is 0.90. In addition, the k_b value provided by ACI 440.1 R-06 overestimated the crack widths of these bars in concrete beam while that of CSA S6-06 was close to the predicted ones.