| Due to the immaturity of the early stage of the rapid development in China's construction industry,many old buildings can't meet the requirements of the existing design specifications,so it is urgent to reinforce the old buildings.At present,the most effective way to rebuild the old buildings is strengthen.Comprehensive analysis of various reinforcement methods,external pre-stressing reinforcement has unique advantages compared with other reinforcement.On the basis of the traditional external pre-stressing reinforcement,this paper makes full use of its advantages and considering its shortcomings.Based on the simple support technology,the external pre-stressing reinforcement of tilted belly poles is presented.According to "Study on seismic behavior of concrete structures strengthened with externally pre-stressed simply supported technology"(based on the seismic performance of the Natural Science Foundation 51468040).The theoretical analysis,numerical simulation and experimental study are carried out to study the effect of externally pre-stressed reinforced concrete beams strengthened with tilted belly poles,the main research contents and conclusions are as follows:(1)Studying the deformation of reinforced beam under uniform load and concentrated load,the formulas for calculating the increment of external cable stress and bearing capacity are derived.The results show that the formula of external cable stress increment has a high accuracy,and the bearing capacity formula has a higher accuracy in the elastic stage,in the shaping stage the accuracy is reduced.Conclusion: the formula of theoretical derivation has higher accuracy,and the formula of bearing capacity in the molding stage should be further studied by nonlinear method.(2)Using ABAQUS software to establish the numerical model of reinforced beam,studying how different cable sag,initial internal force,cable sectional area effect the characteristic loads,the increment of cable internal force and the development of the reinforced concrete beam.The results show that with the cable sag,cable cross-sectional area,cable initial force increases increasing the cracking load,yield load and ultimate load of beams have been increased.The increment of cable internal force increases slowly in the elastic stage,and the growth of the molding stage is rapid.The shape of the strengthened beam is changed compared with that of the unreinforced beam.Conclusion: strengthening technology can improve the performance of reinforcement beams,due to the different factors lead to reinforcement beam shaping and carry out different forms of damage,the construction design should be avoided when the small sectional area,high initial cable force,large sag etc.(3)Taking six simply supported beams as experimental objects,studying the influence of different cable area,cable sag and initial internal force on the characteristic load,failure mode,ductility and reinforcement effect.Through the specific loading to study the stiffness of RC beam changes and cracking.The results show that the characteristic load of the strengthened beam is improved with the increase of the influence factors,the specific loading method can achieve the purpose of strengthening the beam itself,and the corresponding load of the strengthened beam is improved under the same deflection,the ultimate load and the crack distribution of the strengthened beam are all changed.Conclusion: the externally prestressed reinforcement technology of the inclined belly bar increases the stiffness and ductility coefficient of the beam,by changing the stress of the beam,the shear capacity of the shear bending section is improved,and the double purpose of seismic strengthening and bearing capacity strengthening is achieved. |
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