Experimental and Analytical Evaluation of Bond Strength of Reinforcement in Fiber-Reinforced Polymer-Wrapped High-Strength Concrete Beams

摘要

This paper presents the results of two phases of a research program conducted at the American University of Beirut (AUB) to examine the effect of confinement provided by fiber-reinforced polymer (FRP) sheets on the bond strength of tension lap splices anchored in high-strength concrete (HSC) beams. Ten beams with a nominal concrete strength of 68.95 MPa (10 ksi) were tested in positive bending. Each beam was reinforced on the tension side with three 20 mm (No. 6) bars spliced at midspan in a constant moment region. U-shaped FRP sheets were used to externally confine the splice region. The main test variables were the types of FRP sheets: glass or carbon (GFRP or CFRP), the FRP configuration in the splice region (one strip, two strips, or a continuous strip), and the number of FRP layers confining the splice region (one layer or two layers). Except for the epoxy adhesive, no additional anchorage mechanism or bonding procedure was applied for the FRP sheets on the concrete beam. Test results indicated that GFRP and CFRP wraps were effective in improving the bond strength of the lap splices and the ductility of the mode of failure. The experimental results were used to propose a new FRP confinement parameter k_(tr,f) that accounts for the presence of FRP sheets confining tension lap splices in HSC beams. This parameter was calculated based on: area, spacing and ultimate strength of the FRP sheets, and the number and diameter of steel bars being developed.