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Analysis of Shear Lag Effect in Thin Walled Curved Box Girder

Author: PengShiFeng
Tutor: ZhangYuanHai
School: Lanzhou Jiaotong University
Course: Bridge and Tunnel Engineering
Keywords: Curved Box Shear Lag Effect Secondary shear deformation Energy variational method
CLC: U441
Type: Master's thesis
Year: 2010
Downloads: 85
Quote: 0
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Abstract

With a large number of construction of the highway, crossroads and urban viaduct, there has been a lot of curved girder bridges. To Driving smoothly, the need to accommodate linear or ambient conditions, more complex curved girder bridges, which promote the wide application of thin-walled curved box girder bridge engineering. The curve box-type structure to withstand wide beam symmetrical bending load, the wings will shear deformation, resulting in the wing panel normal stress along the width direction was uneven distribution, that is, the presence of shear lag effect. Curved Box included in the shear lag effect brought bending, torsion, shear lag coupling problem, therefore much more complex the curve the box girders analysis than straight box girder. Over the years, many scholars to carry out the research work of the curved box girder To simplify the analysis, early studies often do not account shear lag effect of the curved box girder, while ignoring the shear lag effect, it will underestimate the actual stress of the curved box girder structure Wide Box transverse cracks, resulting overpass or viaduct. Later, the researchers based on the theory of thin-walled bar considering shear lag effect, but omits secondary shear deformation constrained torsion warping displacement, ie the constraint torsional warping generalized displacement is taken as torsion angle The first derivative curve Mechanics Performance is still difficult to get an objective reflection of. This paper presents an improved method for analysis of thin-walled curved box girder for a comprehensive understanding of the mechanical properties of thin-walled curved box girder. Assumptions based on just the surrounding, the basic deformation supplemental deflection shear lag deformation, to consider curve shear lag effect and included in the secondary shear deformation constrained torsion warping displacement. Departure from the self-balancing of the shear lag warping stress conditions, select the shear lag warping displacement mode, with energy variational method to create thin-walled curved box girder deflection torsion control differential equations and boundary conditions. And trapezoidal cross-section of the single-chamber representative single box to box girder, gives a general formula for shear lag warping sectional geometry characteristics. Study showed that: 1, the export of basic differential equations, the first derivative of the torsion angle instead torsional warping generalized displacement, the equation will be transformed into the secondary shear deformation is ignored in the literature of differential equations; The shear lag deformation conjunction ignored, the equation is transformed into the Vlasov equation. Therefore, the establishment of the differential equations can not only promote the Vlasov equation, can objectively reflect the mechanical properties of thin-walled curved box girder. 2, respectively Galerkin method, finite difference method on a Curved Box plexiglass model to solve calculations show good agreement with the theoretical and measured values, in order to verify the calculation method and the correctness of the basic equations of this thesis. Beam shear lag effect of the curve bending method only have a certain effect on the stress had no influence on the warping stress, warping and twisting deformation also has little effect on the bending shear lag effect. Shear lag warping deformation and warping and twisting deformation is basically independent. Simply curved box girder restraint torsion secondary shear deformation effect is generally small, but for a fixed end constraint box girder, cantilever box girder fixed end of its cross-section near the secondary shear deformation effect.

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