Study On The Loss Of Prestress Of Self-anchored Suspension Bridge With Concrete Stiffening Girder And Its Influence

The main cable of PC self-anchored suspension bridge is anchored in the PC stiffeningbeam and the beam will assume the powerful force of the main cable and emerge the elasticdeformation. Therefore, the prestressing tendons in the beam will also produce thecorresponding compression deformation and then generate the loss of prestress due to thehorizontal force of the main cable. Meanwhile, because of the force of main cable acting onthe stiffening girder, time-dependent loss of the prestress in the PC beam will be exacerbatedand the loss due to shrinkage and creep is different from the ordinary flexural main beam,which should be paid certain attention to.This paper summarizes the calculation method of instantaneous loss and time-dependentloss of prestressing tendons with reference to several national norms. According to Code forDesign of Highway Reinforced Concrete and Prestressed Concrete Bridges and CulvertsSpecifications，a PC self-anchored suspension bridge is used to analysis its loss of prestress inthe different position and different stage by establishing its FEM model. Then, comparativeanalysis is carried on between this self-anchored suspension bridge and an ordinarysuspension bridge with the same structural arrangement and sensitivity analysis is conductedon the influencing factors of the loss of prestress. Finally, this paper analyes the influence ofthe loss due to the force of main cable, the time-dependent loss and the long-term effectshrinkage and creep on the alignment and internal force of this kind of bridge. The resultsshow that:1. The prestress loss due to friction and deviation accounts for the majority of prestressloss and it will increase with the increasing of the length of prestressing tendons. The loss ofelastic compression has a certain impact on the total loss and it will increase with theincreasing of the force of main cable. The prestress loss due to the shrinkage and creep is animportant part of total loss and it will increase with the end time delay.2. Compared with the ordinary suspension bridge with the same structural arrangement,the force of main cable of self-anchored suspension bridge changes the stress state ofstiffening girder and causes the growth of the loss due to creep and shrinkage. Meanwhile, it also causes the loss due to the elastic compression deformation of the tendon. The horizontaland vertical force of main cable leads to the external force moment and bending deformationof stiffening girder, which results in the loss due to elastic deformation of the tendon. It is thestress state that makes the loss due to elastic compression deformation and elastic deformationdifferent.3. In the stage of hanger tension and system alteration of self-anchored suspensionbridge，the growth of the horizontal force of main cable provides a free prestress to thestiffening girder. Although the loss of prestress leads to the reduction of axial force of tendons,the increasement of the horizontal force of main cable makes the great growth of the axialforce of the the stiffening girder. The bending moment generated by tendons and the cable hasthe same number in the mid and anchor span while they have different numbers in the sidespans.4. The loss due to elastic compression deformation and the shrinkage and creep ofconcrete causes more influence on the stress state than the alignment of structure.5. The stress state of structure has an apparent redistribution phenomenon due to thelong-effect of shrinkage and creep of concrete and it makes the deflection of main cable andstiffening girder, where the value of deflection increases and its growth rate decreases. Thelong-effect of shrinkage and creep has a significant influence on the alignment and stress stateof structure and the influence will increase while the growth rate decreases with the end timedelay.