The Study On The Static And Dynamic Theory And Practice Of Externally Prestressed PC Beams

External prestressing tendon can improve the stress state of the original beams byactive clamp force; And the simple deviator and the anchorage can less effect on theoriginal beams. Therefore, External prestressing is widely used in practice in old bridgeand disease bridge, to improve the ultimate bearing capacity, and to improve the normaluse performance, and to improve the durability of bridge, and it have goodreinforcement effect.Of externally prestressed reinforced PC beam bridge theory andpractice research, have very important guiding significance in engineering application.External prestressing reinforcement PC beam bridge, the author of this paper do thefollowing several aspects work:The methods for determination of the ultimate stress in external tendons areintuoduced and analyzed, and, both the simplified calculating formulas are summarized.Preliminary analysis suggests that the calculation mode based on the theory of structuredeformation, reflect the characteristic of the coupling between the flexural strength andthe entire deformation in prestressed concrete members with external tendons.The corre-ct calculation formulation of ultimate stress in external tendons can reflect the safetyfactor of external tendons.After studying on the effect of dynamic performance improvement of PC beamwith external tendons, Preliminary analysis suggests that, the external tendons configure-tion shape, and the free length of external tendons, and the eccentricity of externaltendons, and the tensions effective area and the initial tensile forces,are all affect theperformance of external prestressing structure vibration, but the effect was notsignificant; To improve structural rigidity,and to reduce impact effect of the structure, themethod that combining external prestressing with enlarging the bridge deck thicknesscan be verified very effective.After studying on the "Eccentricity decrease effect" as well as the stress amplitudein the use of loads, Preliminary analysis suggests that, the external prestressing structure,in the use of loads, the external tendons "Eccentricity decrease effect" is less pronounced,and limited effects on the structure, so it can be neglected; The stress increment ofexternal tendons in use of loads to meet the requirements of the fatigue performance.