Numerical Simulation And Theoretical Analysis Of RC Beams Strengthened With Non-prestressed And Prestressed FRP Sheets

Being a new structural material, fiber reinforced polymer (FRP) has been widely used in engineering practice for strengthening concrete members, especially in the reinforcement of flexural beams. Most of the researches on RC beams strengthened by non-prestressed and prestressed FRP sheets focuses on experiments and theoretic analysis, while, precise means for numerical simulations are numbered at present. Based on the experimental data of four tests done by Chinese scholars, for RC beams strengthened with non-prestressed and prestressed FRP sheets, the accurate methods of numerical simulations and corresponding theoretical formulas are presented in this dissertation. Concretely the main research work and conclusions are summarized as follow:1. On the basis of plane section, non-bonding slip and non-peeled failure assumption, numerical simulations for RC beams strengthened with Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) sheets are carried out by using ANSYS software. The results of numerical simulations show that the yield and ultimate loads born by the beams are obviously increased. The bearing capacity rises with respect to the increase of layers of FRP sheets in a nonlinear manner. Compared with the ordinary beams, the number of flexural cracks in pure bending segments increases, whereas the space of those cracks degrades greatly. Meanwhile, the deflections of the beams reduce a lot.2. Numerical simulations are provided for RC beams strengthened with prestressed CFRP sheets in the two cases of loaded beam and unloaded beam. CFRP sheets are prestressed by rising the material temperature. The loaded and unloaded beams are simulated by controlling the elements' 'birth' and 'death'. In this case, the flexural performances of the beams indicate that the prestressed FRP sheets can exert high strength properties effectively, and furthermore, it is sound for restraining the spread of cracks and distortion. By this way, the mechanical performance of the beams in serving stage can be improved. The numerical simulations denote that the initial moment weakens the beams' flexural ability, and with the increasing of initial stress, the effect is more notable.3. Error is analyzed by contracting the results of finite element analysis with those of experiments. Since they are coincident well, this numerical simulation can be an effective and convenient way to gain the references for practical projects. 4. Theoretical analysis for the RC beams strengthened with non-prestressed and prestressed FRP sheets is also carried out in this dissertation. According to the fundamental theories of concrete, some formulas are derived for determining the ultimate loads that the strengthening beams can bear. The effects of the layers of FRP sheets and loading history are taken in to account. The comparisons of the results from theoretical analysis and experiments consist well; therefore, the theoretical formulas are creditable for further research.