Study On Shear Lag Effect Of Steel Box Girder Cable-stayed Bridge With Single Tower And Double Cable Plane

The main girders of modern large-span cable-stayed bridges are mostly in the form of flat steel box girders,which are light in dead weight and have good mechanical and stability properties.In this paper,the shear hysteresis effect a systematic investigation of the shear hysteresis effect of the main girder is carried out based on the steel box girder cable-stayed bridge in Dushan Town.The stress distribution of the flat steel box girder cable-stayed bridge under constant load is analyzed by theoretical calculation and numerical simulation,and the stress distribution of the main girders in the construction and operation stages of the steel box girder cable-stayed bridge is investigated by the finite element method,and the actual measured values in the field are compared with the theoretical analysis results.The specific work of this paper is as follows.(1)Firstly,the basic idea of the simulated rod method is introduced,and the formulae for calculating the shear hysteresis coefficient of a flat steel box girder with a flat single box and single chamber is derived.After simplified treatment of the main girder section of the flat steel box girder skew bridge,the shear holdup factor of the main girder of the skew bridge with steel box girder is solved by using the derived formula and combining the limb solution method and the superposition method,and the error was within 5% by comparing with the finite element results,indicating that the derived formula can be applied to calculate the shear hysteresis coefficient of the flat steel box girder cable-stayed bridge.(2)With the help of Midas Civil,a complete bridge model of Dushan Town with steel box girder cable-stayed span was built and the whole construction process was simulated.,and the whole construction process was simulated.Then the detailed structural analysis of the main girder calculation sections in each construction stage and operation stage was carried out by combining the slab unit model established by Midas FEA,and the stress distribution patterns of the main girder calculation sections in different working conditions were obtained.(3)In the present paper,the stress monitoring of the main girders was carried out during the construction of the steel tunnel girder inclined bridge in Dushan Town,and several typical construction stages were selected for spatial finite element simulation analysis.The data measured at the construction site were compared with the results of the spatial finite element analysis,thus verifying the accuracy of the spatial finite element analysis method.(4)In this paper,the effects of the shear hysteresis effect on the cable force,various structural parameters and the transverse position of the load on the flat steel box girder cable-stayed bridge are analyzed and studied.It is concluded that the closer the main girder section is to the cable,the more obvious the shear hysteresis effect is;among the structural parameters,the width-to-span ratio and the presence or absence of cross-sectional spacer have a significant effect on the shear hysteresis effect of steel box girder,and the shear hysteresis coefficient of the main girder section with or without cross-sectional spacer changes by 0.5.The degree of uneven distribution of the transverse positive stress at the pivot point of the simply supported beam changes with the change of the load position.The effects of other structural parameters can be ignored.