Research Of The Mechanics Characteristics And Economic Performance On Suitable Type Of Main Girder Of Cable-stayed Bridges With Different Span

In order to solve the problems that exist in the use of traditional girder types of cable-stayed bridge,Prof.Shao Xudong of Hunan University proposed two new lightweight composite structures.The lightweight composite beam I lay thin-layer UHPC(Ultra High performance Concrete)on the orthotropic steel bridge deck and the lightweight composite beam II is consisted of UHPC waffle deck panel and steel girder.This paper intented to apply the two lightweight composite beams to cable-stayed bridge and analyze its mechanical feasibility、technical and economic performance against cable-stayed bridges with traditional girder types.The main works which were completed are as follows:(1)According to the force mode of cable-stayed bridge,the calculation formulas of material dosage of the cable-stayed bridges with lightweight composite beam were deduced,and the technical and economic performance of cable-stayed bridges using steel girder、lightweight composite beam I and II indenpdently were compared.The calculation results showed that the cable-stayed bridge with lightweight composite beam II had economic advantages over the cable-stayed bridges with steel girder and lightweight composite girder I when the span was less than 1100m;while when the span within 1100m and 1500m range,the initial construction cost of the cable-stayed bridge with lightweight composite beam I was the lowest;after considering the replacement of bridge deck pavement,the whole life economic performance of cable-stayed bridge with lightweight composite beam I was always optimal when the span exceeds 1100m,that is,for cable-stayed bridge with span exceeding 1100m,lightweight composite beam I could replace the steel girder.(2)In order to verify the feasibility of the application of two lightweight composite beams in super long-span cable-stayed bridges,this paper designed three 1100m-span cable-stayed bridges with different main girder types,and established the finite element model for mechnical analysis and economic performance comparison.The results showed that the strength,stiffness and elastic stability of the cable-stayed bridges with steel girder and two lightweight composite beams indenpdently met the standard requirements,and the stress of steel structures of three main girders was at the same level,and the wind resistance of the three cable-stayed bridges was similar.The initial construction cost of the three cable-stayed bridges was very close,and compared with cable-stayed bridge with steel girder,the initial cost of the cable-stayed bridge with lightweight composite beam Ⅰ was reduced by 1%,while the one with lightweight composite beam Ⅱ rised only 4%,so the upper economic-span limit of the cable-stayed bridge with lightweight composite beam Ⅱ was about 1100m.(3)In order to determine the lower economic-span limit of the cable-stayed bridge with lightweight composite beam Ⅱ,a 500m-span cable-stayed bridge with lightweight composite beam Ⅱ was designed.By establishing the finite element model,this paper analyzed its mechanical properties and compared the economic performance with cable-stayed bridges with concrete beam or traditional composite beam.Results showed that:the strength and stiffness of the cable-stayed bridge with lightweight composite beam Ⅱ met the requirements,and the stability of the beam was better for the main girder was lighter.Compared with concrete girder,the lightweight composite beam Ⅱ reduced the weight of the main girder by about 70%,and about 30%when compared with the traditional composite beam,which greatly reduced the material dosage of cables,pylons and foundations.Thus the lower economic-span limit of cable-stayed with lightweight composite beam Ⅱ was between 400m and 500m.