Study On Strengthening Of Rc Component With Efficient External Prestressing

In recent years, with the development of the society, more and more buildings have reached or even out of the design reference period, which need reinforcement and reconstruction. Among the various reinforcement methods, efficient external perstressing reinforcement method has the characteristics of simplicity in construction, definitude in force transmission and convenient in cable replacement. And the perstressing forces could be defined according to the actual situation. So it can make the best use of the high-strength properties of materials, and improve the crack resistance, stiffness and durability of RC structures effectively also. The efficient external perstressing reinforcement technique has become a research hotspot in recent years, and has got broad application in reinforcement engineering.In this paper, a deep study is carried out to further investigate the simply supported reinforced concrete beams which strengthened by efficient external prestressing method through experiment and theory analysis.The monotone loading static test of five specimens was conducted. Thereafter, we contrast and analysis the experiment resuit of the RC beams that flexural and shear reinforced by efficient external prestressing method, including failure pattern, failure mechanism, ultimate bearing capacity, fracture shape, deflection, and so on. On the foundation of the experimental data, some curves was provided, such as load-deflection curve, stress-strain curves of concrete and steel bar, stress-strain curves of concrete and prestressing tendon. Combination of test phenomenons and the curves, this thesis put up the following contrast between beams strengthened by external prestressing and non-reinforced beams: stress and strain changes in section, deformation and crack of the beam, the failure of the beam. The force process of the strengthened beam is described and analysed in detail. According to the results, the author got many valuable conefusions.1. Efficient external prestressing reinforcement technology is available for the flexural reinforcement and shear reinforcement of low intensity RC structures completely, and the reinforcement effect is obvious. Compared to no reinforced components, the load carrying capacity of flexural strengthened components could be increased by 40%, and the improvement of shear strengthened component was about 55%~75%.2. The experiment results also showed that: efficient external prestressing reinforcement technology can improve the crack resistance of RC components effectively. Compared to no reinforcement components, the cracking loads of flexural and shear strengthened components were increased by 42.5% and 27.57%. Efficient external prestressing reinforcement method can suppress the emergence and development of cracks effectively. In the same load, the maximum crack width and height of the flexural and shear reinforced beams can be reduced significantly, and crack resistance performance is improved tremendously.3. Efficient external prestressing method can improve flexural rigidity of components in some extent. The mid-span deflection of flexural reinforcement and shear reinforcement beams were less than no reinforced concrete beams in the same load, and the difference increased with the accretion of the load. When the components destroy eventually, the mid-span maximum deflection of flexural reinforcement RC beams reduced by 21.05% compared to no strengthen RC beam. Compared to no strengthen RC beam, the mid-span maximum deflection of shear reinforcement RC beams reduced by 51.6%and 26.77%.4. Based on existing research results at home and abroad, combined with experimental research and theoretical analysis of efficient external prestressing flexural and shear strengthened RC beams in mechanical behavior, failure modes and failure mechanism, bearing capacity calculation formula of the normal surface and oblique section surface of efficient external prestressing strengthened beams were deduced.5. On the basis of two engineering application examples of efficient external prestressing technology, the general steps of the design are provided, as well as several problems in design and construction should be pay attention to.