箱形梁剪滞效应分析中的广义力矩研究

基于能量变分原理,定义箱形梁剪滞效应分析中与剪滞广义位移相应的广义力,并称之为剪滞力矩,给出其计算公式。从轴向力平衡的力学条件出发,选取剪滞翘曲位移模式,并考虑悬臂板宽度及上下翼板至形心轴距离的影响,使箱形梁剪滞翘曲应力得到更合理反映。根据选取的剪滞翘曲位移函数,导出了剪滞翘曲惯性矩、剪滞翘曲惯性积、剪滞翘曲面积等剪滞几何特性计算公式。最后,对集中荷载和均布荷载作用下,悬臂箱梁的剪滞力矩及附加弯矩的变化规律进行较全面研究,结果表明,剪滞力矩与弯矩具有基本相同的分布规律,但当集中荷载作用于跨内时,在集中荷载作用点至悬臂端梁段内仍有剪滞力矩产生;集中荷载作用下,具有较大跨宽比的悬臂箱梁的附加弯矩分布具有明显的局部性质。

Study on the Generalized Moment in Shear Lag Effect Analysis of the Box Girder

On the basis of the energy variation principle,the generalized force corresponding to the shear lag displacement in shear lag analysis of the box girder is clearly defined and is called the shear lag moment.The formula of the shear lag moment is derived.The shear lag warping displacement mode is chosen upon the axial force equilibrium condition.In order to reflect the stress distribution in the box girder more rationally,the width of the cantilever plate and the distances from the top and bottom flange plates to the centre axis are fully considered.Formulas of the moment of inertia,product of inertia and sectional area for shear lag warping geometrical properties are derived according to the chosen displacement functions.A cantilever box girder under concentrated and uniformly distributed loads is analyzed.All-round analysis of the regularity of distribution of shear lag moments and additional bending moments is accomplished.It is shown that the distribution of shear lag moments and that of additional bending moments are the same on the whole.Shear lag moments still exist in the cantilever box girder between the free end and the loaded section when concentrated loads are applied in span.Additional bending moments in the cantilever box girder with a large span width ratio are distributed locally under concentrated loads.