高架桥弧形底钢结构宽箱梁空间受力分析

Three-Dimensional Analysis of Wide Box Girder with Curved Bottom Steel Structure of Viaduct

高架桥考虑美观采用了弧形底箱梁断面,该钢箱梁结构桥面较宽,宽跨比大,横桥向支撑间距大,受力形式复杂,通过建立空间有限元板单元模型,对桥梁结构进行空间受力分析,以总体把握结构受力特点指导设计。根据计算分析结果可以得出结论:1) 该桥支座附近的腹板比其它腹板受力大,设计时需进行加厚处理,并进行局部稳定分析。2) 荷载作用下,翼缘板有剪力滞现象,其中小跨径结构更为明显,在计算翼缘板正应力时需按有效宽度进行折减。3) 封闭箱室的最外侧边板受力较大,应作为断面腹板进行设计。4) 由于桥梁横向支点间距较大,大跨径支点附近结构及小跨径桥整跨结构横向受力特征均较为明显,需增设横肋系统以加强结构横向刚度。5) 支座位置处顶板、底板均受纵、横桥向两个方向应力作用,需在设计时对相应构造进行加强并使现场焊缝避开最不利受力位置。6) 在活载均布力和集中力作用下跨中翼缘也出现剪力滞现象,设计时应注意对板宽进行折减。7) 若采用平面杆系模型设计时,桥梁中支点应考虑1.3的荷载增大系数,跨中应考虑1.15的荷载增大系数,以确保结构安全可靠。

Considering the beauty of viaduct, the curved bottom box girder section is adopted. The steel box girder structure has wide deck, large width span ratio, large transverse support spacing and complex stress form, Through the establishment of finite element plate element model, the three-dimensional analysis of the bridge structure is carried out in order to master the structural stress characteristics to guide the design. According to the results of calculation and analysis, it can be concluded that: 1) The web near the bearing of the bridge is more stressed than other webs, so it needs to be thickened and analyzed for local stability. 2) Under the action of load, there is shear lag in the flange plate, especially in the small span structure. When calculating the normal stress of the flange plate, the steel plate should be reduced according to the effective width. 3) The outermost side plate of the closed box chamber is under greater stress, so it should be designed as the section web. 4) Due to the large distance between the transverse fulcrum of the bridge, the lateral stress characteristics of the structure near the long-span fulcrum and the whole span structure of the small-span bridge are obvious, so the transverse rib system should be added to strengthen the lateral stiffness of the structure. 5) The roof and bottom plate at the support position are subjected to the longitudinal and transverse stresses of the bridge, so the corresponding structure should be strengthened in the design, and the site weld should avoid the most unfavorable stress position. 6) Under the action of live load distributed force and concentrated force, the phenomenon of shear lag also appears in the middle of span flange, so the width of slab should be reduced in design. 7) If the plane bar system model is adopted in the design, the load increase factor of 1.3 for the middle fulcrum and 1.15 for the middle span should be considered to ensure the safety and reliability of the structure.