Theoretical Research On Concrete Plates Reinforced With CFRP Sheets

Research and practice on reinforcing structure have been carried on for several decades, we have accumulated abundant practical experience in strengthening practice of reinforcing concrete structure, and formed gradually the methods of enlarging column section , pre-tension, bonding steel plate, changing the path of transferring force, jetting concrete and perfusing chemical slurry and so on.Since 1980s', Carbon fiber reinforced polymer (CFRP) has been used to strengthen concrete structure, CFRP has the advantage of less density,larger intensity and convenient construction, so CFRP is being used to reinforce structures extensively. However, at home and abroad the research emphasize on flexural performance and shear strengthen of beams strengthened with carbon fiber reinforced polymer, and also emphasize on the shear strengthen and ductility of columns strengthened with carbon fiber reinforced polymer (CFRP). But fewer papers emphasize on concrete slab . In the paper, flexural strength of slab is studied which is externally bonded with CFRP sheet. On the basis of theory analysis, the calculation method for flexural concrete slab is put forward.The paper is divided into four parts , the results of theory and numerical calculation lead to the conclusions summarized as follow.1) The paper introduce the design theory for concrete slab—yield line analysis ,and analyze the failure type of concrete slab of every support condition . On the basis of analysis, the paper put forward the formula of the ultimate strength for concrete slab with four fixed edges.2) According to failure mechanism of concrete slab strengthened with CFRP sheet, the paper establish the theory for strengthened concrete slab—yield line analysis, and put forward the formulas of the ultimate strength of strengthened concrete slab of every support condition.3) This paper apply the formula of the ultimate strength for strengthened concrete two-way slab, to analyze the effectiveness on the ultimate strength, when we strengthen two-way slab in different range with CFRP.4) The paper establish the finite element model of two-way slab with four fixed- edges, and compare and analyze stress graph and displace graph and crack graph between the slab without strengthening and the slab with strengthening, the results of analysis show that the theory for strengthening is effective.