Investigation of ductility in FRP-reinforced concrete beams

This dissertation addresses the use of pultruded carbon/epoxy FRP (Fiber Reinforced Plastic) rebars as reinforcement for concrete beams and their influence on ductility.; In Chapter 1 a preliminary investigation was conducted using carbon/epoxy FRP rebars to reinforce six concrete beams. Both static and cyclic 3-point bending tests were performed. In order to develop bond between the FRP rebars and the concrete, a single tow of carbon fiber was wrapped around the rods with a pitch of 25 mm (1&inches;). The beams had different amounts of reinforcement to determine the load-deflection behavior. Two additional beams were studied under cyclic loading. These beams demonstrated superior strength, adequate ductility, and excellent retention of stiffness under cyclic loading. This led to a more elaborate test program discussed in Chapter 3.; In Chapter 2 the specimen preparations and the materials used in the tests are discussed. The concrete mix design used in the experiments is given in Appendix A. In order to compare the real strains in the rebar with the strains predicted from a theoretical analysis, a series of static flexure tests using strain gages bonded to the FRP rebars were prepared. The methodology for strain gage applications is described in Appendix B. Pullout tests are also discussed and a value of allowable bond stress was obtained.; In Chapter 3, the effects of several FRP related parameters in the behavior of all the beams were studied. These parameters included: (i) Reinforcement ratio; (ii) Use of steel stirrups for shear reinforcement; (iii) Effect of the addition of 1% polypropylene fibers by volume in the concrete. Properties of this fiber reinforced concrete are presented in Appendix C.; This set of static tests presented either bond or compression failure. All the beams were investigated and compared for their load-deflection, load-rebar strain and ductility. In Appendix D the results for beams using a different overwrap configuration is presented. This modification proved to make the beams more brittle. Predictions for deflections are also included in this Chapter.; The experimental results were evaluated using theoretical analysis procedure initially discussed in Chapter 1, and modified in Chapter 3. This methodology was based on satisfying equilibrium and compatibility using a commonly used nonlinear stress-strain model of concrete.; In Chapter 4, the conclusions and recommendations are presented.