Study On Shear Lag Effect In Box Girder Of P C Cable-stayed Bridge With Single Cable Plane

In bridge structure design, for the lag of web shear transfer in the box girder, there is a shear lag effect in the flange plate. Shear lag effect brings non-uniform stress and adverse effect on box girder. Especially cable-stayed bridge structure is complex, with advancement of the construction stage, structural system changes continuously, after the completion of the folded structure and all cable tensioned, geometric linear and internal force are changed. At completion stage, the cable-stayed bridge structure under the live load is a complicated space problem, under unbalanced load, the torsion and distortion effect makes the force analysis more complex, it is difficult to analyse the box girder with a general theory of computation. Currently the influence of shear-lag effect adopted the effective flange width instead of actual width, but there is no clear regulations on cable-stayed bridge. The foreign regulations of the effective distribution width of flange have detailed provisions, but did not apply to the main girder of cable-stayed bridge, the shear-lag effect of complex structure need further study. Based on fumin bridge, a systematic finite-element analysis and experimental study on shear-lag effect in box girder of prestressed concrete cable-stayed bridge with single cable plane are carried out in this dissertation.Through energy variation method and bar simulation method, the shear-lag effect of box girder was analyzed, and put forward that under the compact-bending load, the shear-lag effect in box girder of prestressed concrete cable-stayed bridge with single cable plane was complex, the shear lag coefficient of box girder related to the ratio of bending moment and axial force. According to the similar theory, the full bridge's mechanics characteristics under construction stage and finished stage were calculated by simulation experiment. The finite element method was used for the three-dimensional anlysis of fumin bridge. the mechanics characteristics and shear lag effect of main girder of the bridge in construction stage are studied under the loads of self-weight, stayed cable and cradle loads. Comparing the model test results and the results of numerical calculation, put forward that at the completion stage, the method by adopting the effective flange width on specification to analyse shear lag effect of main girder was reasonable, the results of numerical analysis were reliable. Determined under the tension cable force in the construction stage, shear lag effect was obvious, away from tension cable, showed that the normal curved box girder web and flange junction characteristics of shear lag was prominent. under the cradle loads, the girder section had a negative shear lag effect. Through numerical analysis, confirmed that at the construction stage, the method by adopting the effective flange width on specification to analyze shear lag effect of main girder was problematic, put forward different location of the beam section using the. different shear lag coefficient to analyse.