Research On Durability And CFRP Sheets Strengthen Steel Reinforced Concrete Beams

With the improvement of people's living standard, people on the requirements of building size have become more sophisticated, which is providing development space for using widely steel-reinforced concrete structure. At home and abroad many scholars study on mechnical behavior and other aspects of steel reinforced concrete structure.But research on the durability of steel reinforced concrete structure is relatively small. Steel reinforced concrete structure as a special kind of concrete structure, its protective layer is relatively thicker than reinforced concrete's, which can protect the steel. However, the bonding properties of steel and concrete are worse than reinforcement and concrete's, which lead to the cracking load of steel reinforced concrete structures less prone to cracks, result in steel corrosion, and thereby reduce the structural life. For this reason, based on the theory of reinforced concrete structures, and combined with the force characteristics of steel-reinforced concrete structure, this paper using the method of combining experiment research, theoretical analysis and computer simulation study on CFRP strengthening pre-splitting steel-reinforced concrete and the durability of steel reinforced concrete structures, etc. Main research contents are as follows:Through the experiment of CFRP strengthening steel reinforced concrete beams, the working mechanism, failure mode and bearing capacity changes of (prestressed) CFRP sheets strengthening steel-reinforced concrete beams were studied. The strain distribution of CFRP sheets, concrete, reinforcement and steel, the deformation of beam and distribution of crack were analyzed.Take into account the initial cracks in concrete, the formula of carrying capacity and ultimate capacity and deformation of (prestressed) CFRP sheets strengthening steel reinforced concrete beams were derived. To verify the correction of bearing capacity and deformation formula, the calculation of bearing capacity and deformation formula compared with the experimental results. Using the method of elastic mechanics and energy, the interfacial bonding properties between prestressed CFRP sheet and concrete were analyzed, the formula of interface shear, slip, peeling stress under the action of the release stress and external loads were established. And the influence of CFRP sheets layer and initial stress on the interface shear, CFRP sheets stress, the slip, peeling stress and axial force were analyzed.Based on theory of the bonding property of corrosive reinforced concrete, the bond-slip performance between corrosve steel and concrete were studied. Using the method of elastic mechanics and energy, the differential equation of interface slip, axial force and member deformation Were established. The calculated formula of interfacial slip, axial force and deformation under different load were analyzed. And the influence of the load, the connected stiffness and corrosive coefficient on them was explored.According to electrochemical principles and methods of elastic mechanics, the calculated formula of corrosive steel was established. Combined with the formula of flexural bearing capacity of steel reinforced concrete beams, the resistance of corrosive steel reinforced concrete beam was analyzed. And application of JC method, the corresponding reliability index was calculated.On the basic of multi-level fuzzy comprehensive evaluation method, the durability of steel reinforced concrete structure was evaluated.Proposed the method of using Markov process models predict the remaining service life of steel reinforced concrete structure. From the two aspects of homogeneous Poisson and non-homogeneous Poisson determined parameter estimation, probability density function, distribution function, reliability function and expectations of the state formula and gave the calculated method of remaining life. And VB language was used for programming, which realizes the visualization of life prediction of steel reinforced concrete structure.