大跨度斜拉桥箱桁组合截面应力分布研究

Study of Stress Distribution on Box-Truss Composite Section for Long-Span Cable-Stayed Bridge

为研究斜拉桥箱桁组合截面主梁纵向应力在横向分布的不均匀性,以及箱桁组合后截面形心下移引起截面应力分布的改变,以沪通铁路长江大桥4线铁路方案为背景,采用精细化有限元分析的方法,对简单荷载工况作用下主梁纵向应力在桥面横向的分布形式,及沿纵向的变化规律开展研究,分析了剪力滞后、形心偏移等因素对主梁纵向应力的影响。结果表明:下弦钢箱除将列车荷载传递给主桁外,也与主桁一起参与结构受力;下弦钢箱底板应力均匀程度较好,顶板横向自弦杆外缘向两侧4m范围应力变化较大。

To study the uneven distribution of the main girder longitudinal stress in the transverse direction for cable-stayed bridges with box-truss composite section and the changes of the stress distribution in the section due to the shift of the section centroid after the box and the truss are combined, the Shanghai-Nantong Changjiang River Railway Bridge with four railway tracks was taken as the study background. The fine finite element analytical method was used to study the distribution pattern of the main girder longitudinal stress in the transverse bridge direction in the context of simple load case and the changing rule along the longitudinal direction. The impact of shear lag and centroid offsetting on the main girder longitudinal stress was also analyzed. The results demonstrates that the lower chord steel box not only takes the responsibility of transmit- ting the vehicle load to the main truss, but also shares the structural load bearing task with the main truss~ the stress in the base plate of the lower chord steel box shows favorable uniformity, while the stress distribution shows great change along the top plate width and the change is greater within the 4 m scope extending from the external edge of the chord.