北京新机场航站楼屋顶钢结构抗震设计研究

Seismic Design and Research of Roof Steel Structure of Beijing New Airport Terminal Building

北京新机场航站楼屋顶钢结构因体量大、造型复杂、跨度大、支承构件数量较少且存在异形柱,成为该工程抗震设计的重点和难点。中央大厅北侧屋盖面积大,同时存在大悬挑,整体结构质心偏向北侧,而屋面标高中北侧高、南侧低,支承北侧屋盖的幕墙柱、C形柱柱高较大,抗侧刚度较小,整体结构刚心偏向南侧,会导致钢结构发生扭转。通过调整支承结构布置,增大北侧屋顶支承结构刚度同时减小南侧屋顶支承结构刚度,有效减小结构质心与刚心偏差,提高结构抗扭刚度,降低结构扭转效应。中央大厅屋顶钢结构由六块主要结构单元通过中心采光穹顶及六道中心放射采光带连为一体,采光穹顶及采光带结构为较轻巧的桁架结构,结构厚度较薄,同六块主体网架结构相比,为整体结构相对薄弱的部位。一旦采光穹顶及采光带结构失效,整体结构成为相互独立的六个结构单元,每个结构单元独立承担各自区域荷载,与整体受力状态相差较大。对结构分块模型进行非抗震组合及设防烈度地震组合下的钢构件承载力验算,结果表明,即使中心采光穹顶及六道采光带结构失效,主体钢结构仍有足够的承载能力不发生倒塌破坏。由于C形柱、钢支撑筒、北侧幕墙支撑框架、独立钢管柱及其他幕墙柱等各类屋顶支承结构构件抗侧刚度差异较大,为提高整体结构在地震作用下的安全性,进行地震作用下的多道防线分析研究。考虑到该工程屋顶钢结构为大跨度空间结构,屋顶支承构件能承担各自负荷质量所产生的地震作用比较合理,对各屋顶支承构件承担重力荷载和地震剪力比例进行分析,对于承担地震剪力比例小于其承担重力荷载比例的屋顶支承构件,按重力荷载比例对其地震剪力进行调整,提高整体结构多道防线抗震能力。通过建立中央大厅结构动力弹塑性时程分析模型,进行罕遇地震作用下的动力弹塑性时程分析,重点讨论屋顶支承钢结构与混凝土结构的塑性变形及其发展程度。结果表明,虽有部分构件进入弹塑性工作状态,出现强度、刚度退化,但退化程度不大,整体结构具有足够的能力进行内力重分布以维持其整体稳定性,并承受地震作用与重力荷载。

The roof steel structure of Beijing New Airport Terminal Building has large volume,complicated shape,large span,small number of supporting members and special-shaped columns,which is the key and difficult point of seismic design of the project.The roof on the north of the central hall has larger area and a large overhang,so the center of mass of the overall structure is biased to the north.However,because the roof elevation is higher on the north and lower on the south side,the height of the columns of the curtain wall and the C-shaped columns which Support the north roof is larger,so lateral stiffness is smaller,and the center of stiffness of the overall structure is biased to the south,which will cause the steel structure to twist.By adjusting the layout of the supporting structures,increasing the rigidity of the roof supporting structure on the north,and reducing the rigidity of the roof supporting structure on the south,it can effectively reduce the deviation between the center of mass and stiffness of the structure,improve the torsional stiffness of the structure,and reduce the torsional effect of the structure.The steel structure of the roof of the central hall is composed of six main structural units which are connected by a central lighting dome and six central radiation lighting belts.The structure of the lighting dome and lighting belts is a lighter and thinner truss structure,which is the weaker part of the overall structure by comparing with the six main grid structures.Once the structure of the lighting dome and the lighting belts fail,the overall structure becomes six independent structural units,and each structural unit bears its own regional load independently,which force state is quite different from the overall structure.By checking the bearing capacity of steel members under non-seismic and precautionary intensity seismic combinations for block models of the structure,it shows that even if the central daylighting dome and six daylighting zones fail,the main steel structure still has sufficient bearing capacity and will not collapse.The lateral stiffness of different kinds of the roof supporting members,such as the C-shaped columns,the steel supporting tubes,the supporting frames of the north curtain wall,independent steel pipe columns and the columns of other curtain walls,is quite different.In order to improve the safety of the whole structure under the action of earthquake,multi-line defense analysis is performed.Considering that the roof steel structure of the project is a large-span spatial structure,it is reasonable that the roof supporting members can bear the seismic force generated by their respective load mass.By analyzing of the proportion of the gravity load and seismic shear force of the roof supporting members,the seismic shear force of the roof supporting member bearing a less proportion of seismic shear force than its gravity load is adjusted according to its proportion of gravity load to improve the seismic resistance of multi-line defense of the whole structure.By seting up the dynamic elastoplastic time-history analysis model of the central hall structure,the elastoplastic time-history analysis of the whole structure is performed under rare earthquakes to discuss the plastic deformation and development degree of the roof supporting steel structures and the concrete structures.It shows that some members enter the elastoplastic working state with their strength and rigidity deteriorated,but the degree of degradation is not large,and the whole structure has sufficient capacity for redistribution of internal forces to maintain its overall stability and bear earthquake action and gravity loads.