| Strengthening reinforced concrete structure with externally-bonded steel plate, glass fiber, carbon fiber, steel mesh and so on, which is a simple and convenient method in direct reinforcement, is widely applied to engineering in recent years, especially carbon fiber is the focus of research and application. At present, there are many different calculated formulas in accordance with different bonded materials. Therefore, those formulas are not very convenient for application, and are very difficult to be compared to select the most suitable one. Although the different bonded materials behave disagreement with each other, Nevertheless, the calculating theory of load capacity is similar. So they can completely enjoy a unified formula. On the basis of this thought, the paper calls this kind of reinforcement as "bonded reinforcement", and mainly studies the universal formula, which calculate the ultimate flexural capacity of the reinforced concrete members, strengthened with externally bonded materials.The paper has concluded the fundamental principle of sticking reinforcement. That is to improve the ultimate flexural capacity of the original reinforced concrete beam through externally bonded with high-strength tension materials.In order to assure the bonded-strengthened beams to have ductility and fully exert the compressive capability of concrete, the paper deduces the lower limit compressive height used in design from the plane section assumption and theory of limit destruction. The lower limit compressive height is when the strain of compressive edge fiber reaches its peak value (0.002) and the externally bonded material reaches its limited strain (0.01). Meanwhile, the design upper limited height is presented by introducing the degree of reliability (shows as table 2.2). Therefore, drawing from the lower and upper limit designed height and steel limit destruction, the paper classifies the design destructive forms of bonded-strengthened beams into three categories ( I , II,III), and gets the relevant integrated formula for calculating flexural capacity and gives therelevant design example of engineering.In order to simplify the calculated procedure, the error coefficient (r1) has beenintroduced to paper. And so, the criterion formula (2.1), which calculates strain and stress in concrete, can be replaced by one-variable formula (2.17). Such simplifiedformula (2.17) cannot only accurately calculate the flexural capability ofbonding-reinforced beams, but its calculated results have definite security.Based on literature and introducing the error coefficient (r2), the paper infers theformula (2.63-2.66), which is applied to calculate the lag strain of bonded materials (Elag) under the secondary load. Through examination, the formula works very conveniently and closely reflects the statue of experiments. Introducing beam's secondary load theory, a series of integrated calculated formula and a designed example that calculate the area of bonded material for strengthening reinforced beams under the secondary load.The bonded-strengthened beams' cracked-moment and yielded-moment can be accurately calculated by introducing the improved algorithm of moment-curvature to paper's program. And the calculated results closely coincide with experimental results. Furthermore, the paper, through applying the improved algorithm to the load-deflection curve and secondary load, also the calculated curves closely coincided with experimental results (showed as chart 3.17-3.20). Meanwhile, the results of program show that, under secondary load, the bonding-reinforced beams' yield-moment would decrease as the original load increase, but the original load wouldn't remarkably influence the ultimate flexural capacity.The paper presents a new comparative method. That is to make the different strengthened forms by externally bonded with different materials reach the same ultimate flexural capacity, and contrast with each load-deflection and moment-curvature curve, which are calculated by paper's...
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