单箱双室简支箱梁剪切变形及剪力滞双重效应分析

Analysis on Shear Deformation and Shear-lag Effects on Twin-Cell Box Girders

基于各个翼板选取不同的最大剪切转角差为剪力滞广义位移,应用能量变分原理分别推导出了考虑和不考虑剪切变形时单箱双室截面控制微分方程组,结合边界条件给出了箱梁纵向应力和竖向挠度的初参数解,从力学、数学角度上证实了剪切变形和剪力滞效应是两个相对独立的力学行为,进一步阐述了二者对箱梁的影响,即剪切变形对箱梁截面纵向应力无影响,但是对竖向挠度有很大的影响.数值算例表明,利用该文解和数值解分析跨中截面剪力滞系数横向分布规律,二者吻合程度良好,其横向分布规律与单室箱梁类似,唯独不同之处是边腹板处的剪力滞效应比中腹板处的剪力滞效应略微大一些;挠度计算表明,剪切效应使得该箱梁在集中和均布荷载作用下跨中挠度分别增大4.6%和2.7%.

Based on the flanges＇ different maximum shear angle differences selected as the shear-lag generalized displacements,the energy variational principle was applied to deduce the shear-lag differential equations for twin-cell box girders with and without shear deformation in consideration,and the initial parametric solutions of the box girder＇ s longitudinal stress and vertical deflection were given according to the boundary conditions.From the angle of mechanics and mathematics it was proved that the shear deformation and the shear lag were 2 relatively independent mechanical behaviors,of which the impacts on the box girder mechanics were expounded：the shear deformation had no effect on the longitudinal stress but had great influence on the vertical deflection.The example of a simply-supported box girder shows that the longitudinal stress at the middle cross section calculated with the presented analytic method and with the numerical method are in good agreement,of which the lateral distribution is similar to that in the case of single-cell box girders;however,the shear-lag effect around the side webs is slightly greater than that around the middle web.The shear deformation adds to the middle deflection of the box girder under concentrated and uniformly distributed loads by 4.6%and 2.7%,respectively.