Studies On FRP-Brick Interface And Its Application

The use of fiber reinforced plastic (FRP) plates or sheets for strengthening masonry structures has already been implemented actually. Indeed, a number of failure modes in FRP-strengthened Masonry Structures are directly caused by debonding of FRP from the masonry. The performance of the interface between FRP and masonry is one of the key factor affecting the behavior of the strengthened structure. Therefore, for the safe and economic design of externally bonded FRP systems, the behavior of the FRP-to-masonry interface needs to be researched. The major contributions of the work presented in this thesis are listed as follows:1. By the shear experiment of FRP debonded from brick interface, the mechanics performance of bonding interface between FRP and fired common brick is researched in detail. The influences of brick compressive strength, bond length and width, layers, types of FRP and type of bonding epoxy adhesives are investigated, and the development and distribution of strain on FRP sheet along the bond length is obtained, The relationship of local bond stress versus slippage is analyzed.2. Based on the experiment results, the values of local bond stress and slippage on the interface are calculated, the relationship between local bond stress and slippage is analyzed, at last, the maximum bonding shear stress formula is proposed.3. Based on the local bond-slip curve obtained in this thesis, two local bond stress-slip models including subsection curves and complete curve are proposed. These models match the experimental results well.4. The debonding process of interface is analyzed, and then, the debonding model of the interface is established. This analytical model is capable of predicting the entire propagation process of debonding. The process of debonding contains four stages: Elastic, Elastic-Plastic, Elastic-Plastic-Debonding and Plastic-Debonding stages. Based on the piecewise, a local bond-slip law, an expressions for the interfacial shear stress distribution, a slip and a normal stress distribution of FRP section are derived for different loading stages. The effective bond length of FRP is defined in the thesis and the analytical solution of the effective bond length is acquired. The debonding process is modeled in detail and the analytical results are compared with experimental data well.5. Based on the derivation of analytical solution, a formula of the ultimate bond load proposed by simplify the solution of governing equations.6. The shear failure mechanism of unstrengthened, strengthened masonry wall and the debonding failure mechanism of strengthened masonry wall are analyzed. Based on a truss model, by taking into account the direct and indirect effect of interface bond force, it is proposed the formula of shear capacity of masonry wall strengthened by FRP, which has an excellent coincidence with the experimental results obtained from the test.