首都博物馆新馆大跨度结构设计中的创新技术

首都博物馆新馆上部大跨度钢结构受力复杂。利用风洞模拟大气边界层气流,对屋盖上、下表面和建筑外墙在各种风向角下的风压分布情况、风环境等进行了测试。在屋盖挑檐的端部设置百叶,有效地减小了长悬臂结构的风荷载效应。从多自由度体系在脉动风荷载作用下的运动方程出发,根据随机振动理论推导出了用于大跨度结构计算的风振系数公式,并考虑了场地类别、结构阻尼比对脉动增大系数ξ的影响。在国内首次采用热完成工艺成型方管作为主桁架的弦杆与腹杆,桁架的腹杆与弦杆直接相贯焊接,为了使设计经济合理,采用了多种方式提高节点的承载力。针对传统柱间预应力支撑体系存在的张拉过程复杂、柱顶偏移不易控制、在柱间桁架下弦杆引起附加轴力等问题,提出在中柱两侧布置人字形拉杆的支撑形式,大大简化了预应力张拉过程,有效避免了柱顶的偏移,减小了柱间桁架下弦的附加轴力。

Large-span Roof Design of Capital Museum's New Building

The large-span roof of the Capital Museum's New Building is very complicated.The wind pressure on outer and inner surfaces of the roof,the outside walls of the building and the wind environment at different wind directions are determined by the boundary-layer wind tunnel test.The persiennes set at the roof end can reduce uplift-wind load significantly.Based on the multi-freedom motion equation of pulsatile wind loads,the calculating equations for the windvibrating factor of the large-span roof are deduced based on the random vibrating theory.The effect of terrain type and damping ratio of the structure to the pulsatile amplifying coefficient are also taken into consideration.Hot finished square tubes are used as chord members and diagonals the first time in China.The chord members and diagonals are welded together directly.Several methods are introduced to increase the bearing capacity of the connections for minimizing the steel tonnage.According to the problems in the traditional tension bracing systems,a new method that the tensioning bars are arranged on the two sides of the middle column symmetrically,is presented.In this way,the procedure of prestressed tension can be easily controlled,the sway of column tops can be avoided,and the additional axial forces in the bottom chord of the trusses can be reduced.