Application Of External Prestressed Technique In Reinforcing Concrete Beam And Study Of Stress Relaxation

In engineering reinforcement, Because of the advantages of simple construction, structural safety ,easy maintenance and economy, the external prestresing technique has been widely used in the new construction of large civil engineering structures. Also, Many engineering structures at service ,such as large span beam and bridges,are suffering from fatigue or structural harm due to structure aging, corrosion of reinfor-reinfor-cement bar and overweight. It is very effective to strengthen these harmed or fatigue structures using the externally prestressing technique.In two decades,as the important part of post-tensioned,the designing theory progress rapidly,but the study of stress relaxation is very little,especially effect among concrete shrinkage ,creep and stress relaxation.The calculation of stress loss,second-order effects,reinforcement design and stress relaxation is studied at large in the paper.Also,a commercial finite element program,ABAQUS,was used to analyse external prestressed concrete beam, the mostly work are follow:Firstly, the factors of stress loss , second-order effects , the increment of stress calculation in detils are introduced. Through analyse the reciprocity relation of external pre-stressed cable and beam,reinforcement mechanism of external pre-stressed cable be studied by using equivalent load theory.Secondly,from the view of numerical simulation , using ABAQUS to analyse external pre-stressed concrete beam,contrast analysis result .the mechanism of action of external pre-stressed cable is discussed by the analysis of stress,strain,deflection and so on which is fore-and-after of concrete simply supported beam of external prestressed of reinforcement; and analyse the reinforcement effect of external prestressed reinforcement ,so that discuss the reinforcement mechanism of external pre-stressed tendons.Finally, On basis of ABAQUS, DevelopingVolt-kelvin model simulate the effect of Stress relaxation. That provide a feasible method for deep studying the effect of stress relaxation to simulating the effect of stress relaxation,to forecasting the changing of reinforcement effect.