Abstract
The goal of the current research was to investigate - using the FE (finite element) modeling - the influence of externally attached CFRP (carbon FRP) U-wraps versus confining steel stirrups on enhancing the bond strength of substandard lap spliced GFRP (glass FRP) bars in concrete beams. The analysis incorporated modeling of the nonlinear response of concrete material and GFRP bars, bond-slip at the interface of concrete with GFRP bars, and contact between CFRP sheets and concrete substrate. Twenty-two concrete beams - internally reinforced with GFRP bars - were numerically studied in flexure. The studied variables involved the amount of confining steel stirrups, the number of CFRP layers, and the gap between spliced bars (0 and 1.5 times bar diameter). Besides two control beams, twenty beams had lap-spliced GFRP bars with a lap-splice length of 40 times bar diameter. Out of the 20 lap-spliced beams, two specimens were tested in flexure after being upgraded with externally attached CFRP laminates for the purpose of calibrating the FE modeling techniques. Based on the FE results, equations were suggested to compute the strain efficiency of the GFRP spliced bars in terms of the confining reinforcement index for both steel and CFRP-confined lap splice.