The Study Of Mechanical Properties Of Externally Prestressed Reinforced Concrete Beams Strengthened

Compared with the traditional prestressed structure systems, externally prestressedstructure, with its numorous advtanges, is widely used in engineering, and has been innovatedcontinuously in recent years. As an active way of reinforcement, externally prestressedreinforcement can effectively improve the shear and flexural bearing capacity of structure as awhole. At present, the research of externally prestressed is more based on the theory ofunbonded prestressed, and seldomly thinks about the effect of the second-order components.In fact, it isn’t coordinating between the In vitro tendon and the beam body deformation of theexternally prestressed structure, which is the main aspect to distinguish the unbondedprestressed concrete structure. So, the influence of the second-order effect on externallyprestressed structure shouldn’t be ignored, and the theory of the unbonded prestressedconcrete structure isn’t totally appropriate for the externally prestressed structure. In view ofthis, based on the existing research results, this thesis, with the covering plate externalprestressing and strengthening of daqin line test as the research background, systematicallyanalyzes the calculation method of external prestressed Liang Yingli increment and deflectiondeformation. The details as follows:Firstly, this paper briefly introduces the research status of the externally prestressedstructure at home and abroad and the commonly used method of the reinforced concretegirder. In addition, it analysizes their reinforcement principles and calculation methods withadvantages and disadvanges respectly.Secondly, this paper, based on the structure’s deformation, deduces the computationalformula of the deflection and stress increment under different steal and different load. Therestlts suggest:1. During the normal stage, the influence of the second-order effect is notobvious, but it becomes obvious gradually with the load continuously increased;2. Setting theexternal steering block can decrease the influence of the second-order effect and improve themechanical properties of externally prestressed structure. With the increase of load, the blockof the beam deflection and stress increment reduce, among which the unidirectional block isthe most obvious one;3. Different load forms influence the deflection and stress incrementdifferently. Under the crossing concentrated load, if the deflection and stress increment is themunimum, the influence on it is the least. Accordingly, the influence of the second-ordereffect is the munimum.Fianlly, it makes the rinforced concrete eternally prestressed reinforcement girder, andis tested in the laboratory during the normal stage. Also, the experiment measures the keydatas of the deflection, the eternal tendon stress increment and so on. In comparison withstrengthening before, after applying different effective prestress, the deflection of the largest decreases by25.2%, the stress increment decreases by13.4%at most, and the strengtheningeffect is obvious.Through experimental comparison, the calculated results of the flrmula in goodagreement with the experimental results. But after the theoretical analysis, the straight linewithout turning second-order effect is larger. So it is not always the most advantageousstrengthening methods. This paper suggests improning it in the future research.