Shear lag effect of U-shaped girder of rail transit considering load types and structural parameters
Aimed at U-shaped girder belongs to open structure,its shear lag effect can not be directly applied to the mature calculation method of closed box girder shear lag effect,the shear lag effect of simply-supported U-shaped girder of rail transit was studied.Based on the background of a subway in Qingdao,the finite element model of space entity and the plane bar model were established respectively.The longitudinal and transverse distribution of shear lag effect of U-shaped girder under three different load types were studied.The variation of shear lag coefficient of U-shaped girder with four kinds of structural parameters were analyzed.The effective width of U-shaped girder were calculated and compared with the current domestic specifications.The results show that train load is the main factor affecting the longitudinal distribution of shear lag coefficient of U-shaped beam,and the shear lag effect is obvious at the position of train wheels.Under the action of the first phase and the second phase of the dead load,the shear lag effect of the simply supported girder is small in the middle section and obvious in the support section.In the transverse distribution of shear lag effect,the shear lag effect at the bed plate of U-shaped girder is more obvious than that at the position of web plate under the action of three kinds of loads respectively.The main structural factors influencing the increase of shear lag effect of U-shaped girder are beam height and floor width,among which the influence of beam height is significant.Increasing the thickness of the bottom plate can effectively reduce the shear lag coefficient of the U-shaped girder,but changing the web thickness has little effect.By comparison and analysis,the current specifications for calculating the effective width of box girder are not suitable for calculating the effective width of U-shaped girder in rail transit.The effective width correction formulas of U-shaped girder is established on the basis of considering the influence of load type and structural parameters,and it is in good agreement with the finite element simulation results.The results can provide reference for stress calculation and reinforcement configuration of U-shaped girder in practical engineering.3 tabs,13 figs,25 refs.
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