Key Technology Study In Construction For Continuous Steel-UHPC Composite Box Girder Bridge

The long span continuous composite girder bridge is more and more favored by bridge workers because of its small self-weight,large span capacity,superior mechanical properties and economic indicators.However,compared with the ordinary girder bridge,its construction is difficult and the overall force of the bridge changes with the change of the construction procedure.Therefore,the determination of rational construction procedure in the construction of long span continuous composite girder bridges has become a crucial part.Based on the 145+254+145m approach bridge of a Yellow River Bridge,this paper studies the rational construction procedure of steel box girder and concrete slab.The main contents are as follows:(1)The basic construction process,advantages and disadvantages,and application range of the commonly used construction methods of steel box girder and concrete slab in the construction of continuous composite girder bridge are introduced.According to the analysis of characteristics of the background engineering,several construction methods of steel box girder and concrete slab are preliminarily determined.(2)Establish the finite element single beam model of the bridge,and determine the optimal construction scheme respectively for the preliminarily determined three kinds of steel box girder construction methods: cantilever+segment hoisting combination construction,full bridge with few fulcrum supports construction and mobile with few fulcrum supports construction.Then the stress in the construction process and in the bridge forming stage of the three optimal schemes are analyzed and compared to determine the rational construction procedure of the steel box girder.(3)By simulating the construction process with or without bottom concrete plate,the differences between double-layer composite beams and ordinary composite beams are explored.Through further analysis of the Peagel method for the initial determination of roof concrete,the longitudinal distribution ratio of bridge deck pouring before and after the removal of main girder support is determined.Considering the construction schedule,the influence of the next construction step on the bridge structure is determined when the concrete of roof and floor are of different ages.(4)Midas FEA was used to establish a local finite element solid model to analyze the influence of the transverse casting sequence of the bridge decks on the stress of the bridge structure,so as to determine the rational transverse construction sequence of the bridge decks.