Study On The Maintainability And The Performance After Maintenance Of Reinforced Concrete Beams

The maintenance, reinforcement and repairing in structure, as a systemic engineering, has been a wild concern in the world. This is a research task with important theories and realistic meaning.On the base of analysis of damage evaluation and reinforcement methods of current reinforced concrete (RC) structures, the paper is mainly conducted to study evaluate the damages with crack width and investigate the effects of carbon fiber-reinforced polymer (CFRP) sheets reinforcement of flexural strength. CFRP sheets reinforcement parameters considered in the analysis are: thickness of CFRP sheets and degree of damages. Some suitable models of RC beams used to simulate the crack width and damaged beams strengthened with CFRP sheets have been made with finite element soft. According to the order of chapter of the thesis, this paper contains such research result as following:1 Describe usual detection methods and evaluating index of the damages of RC structures in China and abroad at present, the state-of-the-art in strengthening technology with CFRP in the world is summarized. Some problems of damage evaluation and strengthening technology in China are put forward.2 The first group (three) simple supported beams strengthened were tested. It was mainly conducted to investigate the deflection, crack width and rebar strains of the RC beams after rebar yielded. With finite element method, the paper gave the simulation results, and some suggestions about RC model were proposed. The paper cited the usual formulas for calculating the crack width of RC structure in good function in China and abroad, explored the relations of the crack width and the deflection, the rebar strains, and made the dependence between the crack eigenvalue and the deflection eigenvalue. It provides academic gist for the evaluating the damage of RC components with crack width instead of the deflection, crack and rebar strains.3 The second group (three) simple supported beams were tested. It was mainly conducted to investigate not only the deflection, crack width and rebar strains, but also the remnant deflection, crack width and rebar strains. The relations of deformation and remnant deformation; crack width, remnant rebar strains, frequency, subsidence ratio and remnant crack width were explored. The drawing of damage evaluation was made. It provides academic gist for the evaluating the damage of RC components with remnant crack width instead of deflection, crack rebar strains, frequency, and subsidence ratio. 4 The third group (five) simple supported beams strengthened with CFRP sheets were tested. It was mainly conducted to investigate the effects of different layers of CFRP sheets and degree of damages on ultimate loads, rigidity, crack propagation, deflection, and press conditions of rebar. The model was made upon that material homogeneous and perfect bond between the concrete and rebar and between the concrete and CFRP sheets are assumed. The model perfectly simulated the flexural performance of beams and gave some systemic datas about flexural performance of beams strengthened with CFRP sheets for analysis and applications. Then, the paper gave the formulas for calculating ultimate loads and rigidity, and the calculation fit well with the experimental data.