| Structural reinforcement is aimed at structural failure due to functional changes,structural aging and engineering quality accidents(design errors,unqualified raw materials,etc.).In many reinforcement methods,the external prestressing technique has the advantages of eliminating stress lag and reducing the self-weight of reinforcement material.It is widely used because of its small influence on the clearance of the structure and the remarkable improvement of the bearing capacity of the beam.Because the concrete beams strengthened by external prestressing with steel strands can not reach the yield strength of the steel strands,Waste of materials.This paper focuses on structures or components under the condition of certain load,the reasonable tensile force is applied to the ordinary reinforced,so that the reinforced at the bottom of the beam and the prestressed bar in the external force can simultaneously reach the yield stress of the reinforced in the process of loading.It can provide important theoretical basis for the practical reinforcement of building.In this paper,through theoretical analysis and calculation of stress increment of externally prestressed reinforced,combined with ANSYS software to simulate RC beam strengthened with external prestressing force of ordinary reinforced,and to carry out experimental study,the results of calculation and test are coMPared.The main tasks are as follows:(1)On the basis of existing theoretical formulas,considering the influence of the secondary effect on the external prestressing strengthening system,through the analysis of the bearing capacity of the reinforced concrete beams strengthened by external prestressing,the analysis and calculation of the deflection of the beams,the analysis of the short-term stiffness of the strengthened beams.Based on the analysis and calculation of the relationship between the increment of external prestressing bar and the extension of external tendons,a simplified formula of the initial tension applied to the externally prestressed reinforced concrete beams is derived.(2)ANSYS software is used to simulate the whole process of loading on reinforced concrete simply supported beams strengthened by external prestressing of ordinary reinforced,and the reasonable finite element model is selected to apply the initial tensile force to the external prestressed tendons.By changing the initial tensile force continuously,the reinforced in the beam and in vitro can reach its yield strength simultaneously.After the simulation,the results of each simulated beam are coMPared with the calculated results of the theoretical formula.The feasibility of the theoretical formula and the effectiveness of external prestressing reinforcement of ordinary reinforced are obtained,and the initial prestress of RC beams strengthened by external prestressing is further discussed by changing the parameters of concrete beams strengthened by external prestressing.(3)Through the calculation of theoretical formula,the initial tensile force of the external reinforced of each test beam is obtained,and the experimental study is carried out.The mechanical properties,failure form and stress change of the reinforcing beam in vivo and in vitro are analyzed,and the experimental results are coMPared with the calculated results.Further verify the feasibility of the theoretical formula.The study shows that the initial tensile force of the external reinforcement calculated by the theoretical formula is applied to the reinforcement bar outside the strengthened beam,and the static loading test shows that: coMPared with the unstrengthened beam,RC beams strengthened by external prestressing of ordinary reinforced can obviously improve the bearing capacity of RC beams,control cracks effectively,improve the overall mechanical and deformation properties of beams,and verify the feasibility of the theoretical formula.It provides a reliable theoretical basis for the external prestressing reinforcement design of ordinary reinforced. |
