Embedded Fiberboard Bar - Concrete Bond Constitutive Model And Its Application Research

Near-surface mounted (NSM) CFRP reinforcement is a new technique for the strengthening concrete structures with CFRP. It not only keeps the advantages of the externally bonded CFRP reinforcement, but also offers additional practical improvements, such as simple construction process, good properties of effective strengthening on the deck of negative moment and full utilization of high strength. Its critical issue is the bond between FRP strip and concrete. In this paper a new type of pull-out test set-up with C-shaped specimen is devised to study the bond behavior on the interface of CFRP plates and concrete. Such test can reduce the influence of eccentricity. The local bond-slip relationships are also discussed on basis of the load-slip relation measured from the test and a constitutive model is suggested by analysis. And the test gains the conclusion such as:1. Experiment study: These are 24 C-shaped specimens in test. The effect of bond materials bond length, concrete strength and dimension of the groove on bonding interface is experimentally investigated. The test result shows that the pull-out load increases when these parameters grow. The major effect comes from bond length and the minor from concrete strength.2. Theory investigation: On the basis of analysis of test data, the load-slip curve and the eigenvalues in load-slip curve are found out, and the theoretic expression and program is coincident with experimental results well.3. The nonlinear analysis of strengthened beam: On the basis of analysis of load-slip curve, the relation of load and deflection is invest -igated in the NSM strengthened beam. The constitutive relation is applicable further.