北京北站站台大跨度张弦桁架雨棚设计研究

Design and Research of the Long-Span Truss String Structure for the Platform Canopy of Beijing North Station

针对北京北站站台大跨度张弦桁架雨棚结构设计中抗风、抗震、温度作用以及支承柱稳定等难点问题,采用有限元法进行各种荷载组合工况下雨棚结构的受力分析。结果表明:张弦桁架构件的设计主要受活载参与组合工况控制,而支承柱及其基础的设计则受地震作用参与组合工况控制;风荷载的作用使拉索索力减小,当拉索完全松弛后,张弦桁架的受力性能会发生质的下降,通过优化张弦桁架的矢高和垂距、桁架断面高度以及拉索截面积等参数,可提高雨棚结构的抗风性能;支承柱的刚度会直接影响雨棚结构的失稳模式和稳定承载能力,设计时应保证支承柱不先于上部的张弦桁架发生失稳。研制的2种新式铸钢节点有效地解决了拉索节点受力大、构造复杂等设计难点。

Wind resistance, seismic resistance, temperature action and the stability of support columns are the difficult problems in the design of long-span truss string structure for the platform canopy of Beijing North Station. With finite element method, the mechanical performances of the canopy structure were ana- lyzed under various load combinations. The results show that, the design of the components for truss string structure is mainly controlled by live load combination condition. While the design of support col- umns and foundation is controlled by seismic load combination condition. Cable force can be reduced under wind load. The mechanical properties of truss string structure will be weakened significantly while the ca- ble completely loose. The win＆resistance performance of canopy structure can be improved through opti- mizing the vector height and vertical distance of truss string structure, the height of truss section and the sectional area of cable, etc. The Buckling modes and stable bearing capacity of canopy structure are direct ly affected by the stiffness of support column. Failure of the support column before the truss string struc- ture above should be avoided in the design. Two new types of cast steel joints are developed, which can ef- fectively solve such design problems as large mechanical force at cable joint and complex structure.