Research On Reasonably Completed State And Design Parameters Of Partially Cable-stayed Bridge

Partially cable-stayed bridge is a kind of partially cable supported girderbridges.Viewed from the girder bridge point,it makes the span which can not achieve bygirder itself meet design requirements with assists of cables.And viewed from cable-stayedbridge point,instead of the mind that girder is a supporting role even the capacity of it isnot cosidered,it takes girder as the main structure but cables as the assistant part.Based onthe design concept of partial cable support,both girder and cables of a partiallycable-stayed bridge carry a portion of the entire load.It uses cables to impart additionalstrength girder itself can not be able to carry. By comparison with general cable-stayedbridges, partially cable-stayed bridges have special advantages:on one hand, the capacityof the girder itself and the cable supports can be fully utilized.It helps to reduce costs andachieve greater efficiency.On the other hand,stay cables only impart a portion of load topylon,which makes a considerable mobility for the size and style of pylon components.Because of the upholding to the design principles of economy and aesthetics, partiallycable-stayed bridges have great potential. In view of these described above,it studies thereasonably completed state and design parameters of partially cable-stayed bridges basedon the engineering of xin cheng dong jie bridge which is a partially cable-stayed bridgewith “V” type arch-tower as follows:Firstly,it explains the origin of partially cable-stayed bridge by extending partiallycable supported girder bridges.And it points that during the design of cable-stayed bridgeswith medium and small spans(no more than250m),it fully considers the capacity of thecable and girder among which girder is the main loadbearing part and cable is anassistant.The capacity of the girder itself and the cable supports can be fully utilized in theoperation stage of bridges which makes a girder bridge that by itself would not be able toattain a given span length satisfy the design requirements.The cable-stayed bridge designedwith the concept above is called partially cable-stayed bridge.Secondly,it studies the structure analysis theory of cable-stayed bridge overally anddeeply.It also analyses the features of every structure system and the theory of plane frameand space structure.Then it summaries the principle and methods of cable force optimization for cable-stayed bridge.Thirdly,it builds a finite element model of the main part of the bridge engineeringbased on in this paper by the software of Midas/Civil7.95and with the principle that bothcable and girder carry50%of dead load in the state of completed bridge,it determins areasonable state of completed bridge through cable force optimization by the method ofminimum bending energy with controlling stress threshold of girder sections.It concludesfrom the analysis of the completed state determined that geometry,cable force and innerforce when bridge is completed agree with the ideal condition which also satisfy everyrequirement of associated codes.Besides,it achieves the goal that both cable and girdercarry50%of dead load in the state of completed bridge.Fourthly,it studies the laws about effects each of five design parameters includinggirder rigidity,pylon rigidity,cable rigidity, length without cable in the end of girder and tiltangle of pylon to each of five load effects including the longitudinal displacement of thetop of pylon, the bending moment of the bottom of pylon,the maximum deflection of girderwithin cables,the maximum positive bending moment of girder within cables and thenegative bending moment in the place of girder support. In the item of cable rigidity，research on laws about effects to cable force in the state of completed bridge is added.Fifthly,it summaries the conclusions and the shortcomings in this research.The study results about reasonably completed state and design parameters of partiallycable-stayed bridge may provide references for the design of bridges of the same kind andit also can promote the application and development of partially cable-stayed bridges.