The Construction Contol Technology Of The Precasting And Assembling Separated Concrete Box Girder Of Long Span Hybrid Girder Cable-stayed Bridge From Aerial Work Platforms

Cable-stayed bridge, is one of the most commonly used bridge with long-span, which often adopts unsymmetrical structural system with hybrid girder and high-low tower to satisfy the requirement of the geologic-conditional character of bridge location and the needs of the economy and utility design . Hybrid girder cable-stayed bridge is a kind of bridge that the main girder is made from two different kinds of materials. The girders of main span are steel girders, and the beams of side span(or adding part of the main span) are prestressed concrete beams.This prestressed concrete box girders of side span are usually precast and assembled with short-line match method. The article is based on the concrete box girder construction of the south span of the JingYue YangZe River Highway Bridge. Through the site observation and calculation for deformation(such as warp, etc.) in the process of the girder precasting and assembling, and also imitation for deformation of girder section by ANSYS finite element software, the problems showed up during the girder assembling have been analyst and solved . The main contents and results of this paper is as follows.(1)The precast construction of PC box girder sections in South span by short-line method, use high altitude multi-platform as beam precasted at the same time. The precasting of joint connect on each platform,has utilized wet-joint metheod to realize seamless link, which solve the match problem of precasting and assembling between different platforms, and guaratee the smoothness of the whole line-shape.(2) Short-line matching metheod is a process of repeating circular. Through the analysis and comparation of actual measurement and theoretical value of the girder, the control data of next cast-in girder will be adjusted in time. It avoids the error which would probably accumulate to the next girder data.(3)Positioning of the matching-sections is the most important sector of construction with short-line matching method. It extrapolates the three-dimensional coordinate of the sleeve and soleplate of the next cast-in girder by geometric control method, which provides the theory basis for its accurate positioning.(4) Through the analysis from actual measurement at its current state, the girder section had the warp distortion on the vertical direction. Based on this, both adjusting the wide difference of the roof and floor, and improving the design of shear,are the effective measures, these have greatly improved the schedule and quality of girder assembling , and these also ensure that the actual line-shape is close to academic line-shape.(5)From the analysis of the bridge seat connection failure problem which were caused by the roughness of the orbit during the girder erection with ANSYS program, we know, on this occasion, it will cause the box girder sections to crack.(6)Concrete girder in south span relates to dismantling temporary brackets. It mentions three ways of dismantling the temporary brackets in side span. Through the theoretical caculation to stress, deflection and cable forces, we can conclude that the best proposal is dismantling temporary brackets by spans and sections.