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.