Structural Behavior Of Long-Span Steel Arches With Variable Box Sections

The Beijing Capital International Airport Terminal 3 is a continuation project for 2008 Olympic Games, and the Ground Transportation Center (abbr. GTC) is an important part of this project. The roof of GTC adopts long-span steel arches with variable box sections. This thesis is grounded on GTC and carries out relevant research on mechanics properties, stability behavior and seismic response systematically and deeply.The practical application and theoretical research of arch structures are first reviewed, followed by a brief introduction on the capital airport project, the formation and the structural layout of the GTC roof, and the load cases considered in the project.Each single arch in the in the GTC roof is modeled as a two-hinged arch, which is a one-order redundant structure. The static solution of the arch under uniformly distributed vertical pressure is resolved, and the basic formulations for the in-plane and out-of-plane buckling are derived. An example is provided to compare the results of in-plane and out-of-plane buckling from theoretic solution and numerical method.The total 13 pieces of arches are devided into 4 groups according to their spans and locations, and the arch whose span is the longest in each group is analyzed with finite element method. On the basis of the linear stress analysis and the eigenvalue buckling analysis, the equilibrium paths for both the limit point buckling (snap through) and bifurcation buckling are traced successfully by geometrically nonlinear analysis. Moreover, the effect of initial geometric imperfections on the stability of the single arch is investigated, and the behavior of arches with variable sections and corresponding constant sections is compared.The box-arch shell structure without the movement joint is selected as the structuralsystem of the GTC roof, which is also the structural model analyzed in this thesis. Linear stress analysis, eigenvalue buckling analysis and geometrically nonlinear analysis are carried out, and the effect of initial geometric imperfections is studied. It has been shown that this structure is very sensitive to initial imperfections, and the existence of the imperfection leads to a significant reduction in the stability load-carrying capacity. In addition, in imperfection sensitivity analysis on structures subjected to unsymmetrical loading with eigenmode-affine imperfections, the selection of the imperfection pattern should consider the distribution of the applied load. Otherwise the imperfection may strengthen the structure.The vibration characteristic of the structure is also analyzed. The dynamic behavior under the common earthquake is investigated by the response-spectrum method and the time-history method respectively and the distribution of dynamic internal forces is obtained. The results from the two methods are compared.