Research On The Coupling Effect Of Long Section Box Girder And Formwork Bracket Of Cable-Stayed Bridge

With the rapid development of bridge construction technology in China,the translational construction method has matured.The concrete swivel cable-stayed bridge is generally constructed by cast-in-place before the turning.The prestress effect causes the deformation of the cast-in-situ beam to be bound by frictional resistance caused by the contact between the formwork bracket and the cast-in-situ beam,which makes it difficult to reach the design stress.Tensile prestressed tendons cause load and weight distribution of cast-in-place beams,and there are certain hidden dangers to the stability of the support.Therefore,it is necessary to study the contact coupling between the cast-in-place beam and the formwork bracket.This paper relies on a cross-rail swivel cable-stayed bridge,establishes the contact coupling model of long-segment box girder and formwork bracket through the finite element software ANSYS,and applies the prestressed steel beams in different parts to different working conditions according to the specific construction sequence.There are two aspects: on the one hand,the effect of friction caused by the coupling of the box girder and the formwork bracket on the stress and displacement of the box girder;on the other hand,after the load and weight distribution of the box girder,the stability of the bracket is checked.The details are as follows:(1)Assuming that the friction coefficient between the box girder and the formwork is 0,0.03,0.1,0.3,0.6,the longitudinal prestressed steel beams of different working conditions are sequentially stretched to compare and analyze the stress and displacement changes of the box girder.Studies have shown that under the same working conditions and different friction coefficients,the friction effect causes the central compression stress of the box girder floor to decrease,the longitudinal displacement decreases along the bridge,and the vertical displacement increases,which has no obvious effect on the central stress of the box girder roof.With the increase of longitudinal prestressed steel strands,the effect of frictional resistance on the stress and displacement of box girder also increases.(2)By sequentially tensioning the transverse prestressed steel beams in different parts,the transverse stress and displacement variation of the box girder are compared and analyzed.The research shows that under the same working conditions and different friction coefficients,the friction effect causes the transverse tensile stress of the box girder floor to increase,the compressive stress decreases,the vertical displacement at the transverse center of the floor increases,and the two ends decrease.(3)Friction effect will cause insufficient effective prestressing of the box girder.When the friction coefficient reaches 0.3 or greater,the influence of the friction effect on the stress state of the box girder cannot be ignored.During construction,measures should be taken toreduce the friction coefficient as much as possible to avoid potential safety hazards to the bridge.(4)After tensioning the transverse prestressed steel beam,the load and weight distribution of the box girder occurs,and the force of the bracket changes.Check the stability of the bracket after pouring concrete and in this case.Studies have shown that the tensile prestressed steel beams,the formwork,primary and secondary keels,uprights,and concrete cushions on both sides of the chamber to the chamfer are increased,which adversely affects the stability of the bracket.All parts of the bridge supports meet the requirements of the design specifications,and the support layout and calculation schemes can provide reference significance for the same and similar bridges.