Seismic Design Study on Roof Steel Structure of Beijing New Airport Terminal Building

The roof steel structure of Beijing New Airport Terminal Building has become the focus and difficulty of the seismic design of the project due to its large volume, complex shape, large span, small number of supporting members and the existence of shaped columns. The roof cover on the north side of the central hall has a large area, and at the same time, there is a large overhang, and the overall structural center of mass is biased toward the north side, while the roof elevation is high on the north side and low on the south side, the curtain wall columns supporting the roof cover on the north side and the C-shaped columns have a large column height, and the lateral stiffness is small, and the overall structural center of mass is biased toward the south, which will result in the torsion of the steel structure. By adjusting the arrangement of the supporting structure, the rigidity of the supporting structure on the north side of the roof is increased while the rigidity of the supporting structure on the south side of the roof is reduced, which effectively reduces the deviation between the center of mass and the center of rigidity of the structure, improves the torsional rigidity of the structure, and reduces the effect of torsion of the structure. The roof steel structure of the central hall consists of six main structural units linked together by the center light dome and six center radial light belts. The light dome and light belt structure is a lighter truss structure with a thinner structural thickness, which is a relatively weak part of the overall structure compared with the six main frame structures. Once the light dome and light belt structure fails, the overall structure becomes six structural units independent of each other, each structural unit bears its own regional load independently, which is quite different from the overall stress state. The results of the bearing capacity calculation of the steel members under the non-seismic combination and seismic combination of the intensity of protection for the structural block model show that even if the center light dome and the six light belts fail, the main steel structure still has enough bearing capacity not to collapse and damage.
Due to the large difference in lateral stiffness of various types of roof supporting structural members such as C-shaped columns, steel supporting cylinders, north curtain wall supporting frames, independent steel pipe columns and other curtain wall columns, in order to improve the safety of the overall structure under seismic action, the analysis and research of multiple lines of defense under seismic action is carried out. Considering that the roof steel structure of the project is a large-span space structure, it is more reasonable that the roof supporting members can bear the seismic effects generated by their respective load masses, and the proportion of gravity load and seismic shear force borne by each roof supporting member is analyzed, and the proportion of seismic shear force borne by each roof supporting member is smaller than the proportion of gravity load borne by each roof supporting member, and the seismic shear force of each roof supporting member is adjusted according to the proportion of gravity load, so as to improve the seismic capacity of the overall structural multichannel defense. The seismic capacity of the overall structure with multiple lines of defense is improved.
By establishing the structural dynamic elastic-plastic time-course analysis model of the Central Hall, the dynamic elastic-plastic time-course analysis under the action of rare earthquakes is carried out, focusing on the plastic deformation of the roof-supporting steel structure and the concrete structure and their degree of development. The results show that although some members enter the elastic-plastic working state and degrade in strength and stiffness, the degree of degradation is not significant, and the overall structure has sufficient capacity to redistribute internal forces to maintain its overall stability and to withstand seismic and gravity loads.