Study Of Prestressed Carbon-fiber Reinforced Plastic In Strengthening RC Beams

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 basises on non-bonding slip and non-peeled failure assumption.While,the researches on RC beams strengthened by non-prestressed and prestressed FRP sheets basises on bonding slip and peeled failure assumption are numbered at present researches.Based on the experimental data of eight tests RC beams 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.The main research work and conclusions are summarized as follow:1.The paper introduces the present RC beams strengthening methods,concludes the advantage and the disadvantage of RC beams strengthened by the non-prestress CFRP sheets and the prestress CFRP sheets. Meanwhile,the Paper describes the failure modes of the strengthening RC beam and simply introduces the present experimental study,theory study and finite element analysis application in domestic and foreign to emphasize the importance of the prestress CFRP sheets for RC beams strengthening.2.According to the material property disadvantage of CFRP sheet,the group is committed to research and development an innovative anchorage by long-term try and many experiments for anchoring CFRP sheet are researched.3.On the basis of numerical simulation theory,the paper describes the material property of the concrete,steel,CFRP sheet and mucus layer,and chooses the element type according to the components of the RC beams strengthened by CFRP sheets. Especially,the paper chooses the element SOLID45 to modify the mucus layer to build the analysis model.4.On the basis of bond-slip relationship between CFRP sheets and concrete surface,the test RC beams strengthened with CFRP are calculated by ANSYS finite element analysis according to the interface bond-slip. The paper conducted to the comparison between results of experiment and element simulation.The results of comparison between experiment and element analysis show that the results of experiment is similar to those of models. 5. On the basis of bond-slip relationship between CFRP sheets and concrete surface, the test RC beams strengthened with prestress CFRP are calculated by ANSYS finite element analysis according to the interface bond-slip. CFRP sheets are prestressed by rising the material temperature and controlling the elements'"birth"and"death".The paper conducted to the comparison between results of experiment and element simulation. The results of comparison between experiment and element analysis show that the results of experiment is similar to those of models.Finally,the paper also conducted to the comparison between results of the RC beams strengthened with prestress CFRP and the RC beams strengthened with CFRP. The results of numerical simulations show that the flexural performances of the beams indicate that the prestressed FRP sheets can exert high strength properties effectively. By this way, the mechanical performance of the debonding failure for the RC beams strengthened with non-prestressed and prestressed CFRP sheets is also carried out in this dissertation.6. Theoretical analysis of debondinncrete and the present researches,some formulas are introduced and the best prestress level are derived for determining the debonding failure loads that the strengthening beams can bear.