Study On The Static And Dynamic Performance And Parameter Analysis Of The Composite System Of Variable Section Beam And Self-anchored Suspension Cable

The combination system bridge of variable section beam and self-anchored suspension cable bridge has a graceful shape combining rigid-softness,and has both functional and aesthetic functions.This composite system bridge can solve the problem of long-term down-warping in the operation process of girder bridge,and have the advantages of long-span capacity of suspension bridge and high rigidity of continuous girder bridges.In the future,it has a broad development.This paper makes research about static,dynamic performance and parameters of the first combination system bridge of variable section beam and self-anchored suspension cable bridge?Luobu River Bridge adopting the method of analysis of finite element in detail.Firstly,the structural design of Luobu River Bridge is introduced,and the rationality of this scheme is illustrated by comparison on two different schemes.The finite element software is used to build a finite element model in detail,and six load combinations are selected to check that the structural stress meets the requirement of specifications under the most unfavorable load combination.The advantages of the composite system are obtained by comparing it with continuous beam and self-anchored suspension bridge.It's illustrated that deflection of the mid-span of the composite system is less than continuous beam bridge or self-anchored suspension bridge by comparing it with the two different bridges.Six structural parameters,such as rise-span ratio and ratio of side to main span,were selected to study the influence of each parameter on the static performance of composite system under the action of dead load or live load.The research demonstrates several change regularities:(1)with the decrease of rise to span ratio,the cable tension and deflection of the mid-span increase,tensile force of rod decreases;(2)with the ratio of side to main span increase,the cable tension of side span decreases,the cable tension of main span has a small change;(3)with the tensile stiffness of main cable increase,the cable tension increases and bending moment decreases;(4)with bending stiffness of stiffening girder increase,the cable tension decreases and bending moment increases;(5)with height of main tower increases,the cable tension and bending moment increase;(6)with the derrick spacing increases,tensile force of rod and bending moment increase,the cable tension decreases.These change regularities have certain reference significance for the design of the same type of composite system bridge in the future.The dynamic characteristics of the composite system and the influence of four parameters,such as rise-span ratio and ratio of side to main span,on the dynamic characteristics of the composite system are analyzed.It's discovered that the first ten natural frequencies of the composite system are more bigger than them of self-anchored suspension cable bridge.The increase of rise-span ratio makes the frequency of the first five modes increase;the increase of the ratio of side to main span makes the frequency of the first five modes decrease;the increase of bending stiffness of stiffening girder makes the first,the fourth and the fifth frequencies increase,and the second and the third frequencies remain essentially unchanged;the increase of derrick spacing has a little influence on free vibration characteristics.