Analysis Of Interactions Between Subgrade And Foundation And Superstructure Of Mega Frame Core Tubular Structure Of Super Tall Building

The mega frame core tubular structure of super tall building, which can be classified as the mega frame core tubular structure without diagonal bracing and the mega frame core tubular structure with diagonal bracing based on the outer mega frame, is one of well-known new structural systems for super tall buildings in the century. This structural system has a good spatial working performance since its each structural member will work together to resist loads applied on it. The superstructure and its foundation of the system are simplified equivalently and continuously into a combination of stiffened-thin-walled tubes on seim-infinite elastic subgrade. Then a semi discretization is made by some longitudinal nodal lines, the unknown deformation functions defined on the lines are used as primary unknowns, and interpolating functions are implemented between the lines. Thusly, the displacement field or motion field of the stiffened-thin-wall tubes could be expressed by the generalized coordinates. Based on principle of minimum potential energy or Hamilton's principle, the interactions between the subgrade and the foundation and the superstructure or the free vibration analysis equations can be obtained, which are actually a group of ordinary differential equations and can be solved by ODES (Ordinary Differential Equation Solver). By means of analyzing the results of computing examples, some reasonable and significant conclusions are obtained and these imply that the simplified semi-analytical model is reasonable and feasible, which provide an feasible analytical method for project design and initial design and earthquake-resistance conceptual design and the whole property evaluation of the super tall buildings adopting the mega frame core tubular structure without diagonal bracing and the mega frame core tubular structure with diagonal bracing. The principal creative work of the thesis are as follows:1. The development of the mega frame core tubular structure of super tall buildings and the necessity and significance to analyze this mega structure with the semi-analytical method are discussed.2. The various equivalent stiffness equations of the semi-infinite elastic subgrade, corresponding to the various deformations, are formulated by employing principle of energy equivalence and Mindlin's displacement equations in a semi-infinite elastic body due to one concentrated force acting in the interior of the semi-infinite elastic body. By using these equations, the interactions between the subgrade and foundation would be easily determined quantitatively.3. The three-dimensional semi-analytical model, which is the combination of the subgrade and the foundation and the superstructure of the mega frame core tubular structureof super tall building; are developed, including the discussion of how to idealize the superstructure, the foundation and the subgrade continuously; and how to choose the unknown function or generalized coordinate of the displacement or motion to describe the behavior of the structure due to the action of various loadings;4. The interactions between subgrade and the foundation and the mega frame core tubular structure without diagonal bracing and the mega frame core tubular structure with diagonal bracing of super tall buildings under static loads have been computed by semi-analytical method. And the multidimensional free vibration analysis of the mega frame core tubular structure with diagonal bracing of super tall buildings is also studied. The tendency of the static characters and dynamic characters of the structure are lucubrated when the main design parameters are changed.