Study On Lateral Resistance Mechanism Of Mega-Braced Frame-Core Tube Buildings

Since the 21 st century,the upsurge of super high-rise building construction has sprung up all over the world,especially in China.The new structure system with mega-braced frame-core tube is widely used.Based on the equivalent continuum model and the stiffness principle,mega-braced frame,core tube and mega-braced frame-core tube buildings under lateral load are systematically studied,including the mechanical characteristics,deformation characteristics,material consumption and stiffness degradation.The main contents are as follows:In this thesis,the stiffness matrix of the mega-braced frame structure with equal section is derived.The bending stiffness and shear stiffness of the structure are solved and simplified,and the lateral displacement and internal force of the structure are obtained and verified by numerical method.The design method based on the stiffness principle is introduced and used to analyze the mega-braced frame structure with variable cross-section.The concept of the ratio of bending-shear displacement s is proposed and the parameter is studied.When s is between 1.2 and 1.8,the structure is more economical and reasonable.In this thesis,the equivalent bending stiffness and shear stiffness of the core tube structure with coupling beam are derived,and the lateral displacement and internal force of the structure are obtained and verified by numerical method.A method for calculating the core tube’s overall stiffness coefficient γ is proposed and the parametric study of the overall performance of the core tube is carried out by using the overall bending moment coefficient and coupling ratio.This thesis introduces the principle and application of the reduction of the rigidity of the coupling beam and analyzes its influence on the integrity of the core tube and the internal force of the coupling beam.The equivalent lateral stiffness of the core tube is simplified and the bending deformation and stiffness distribution of the core tube are deduced by using the design method based on the stiffness principle.A simplified model of mega-braced frame-core tube structure is established in this thesis.The lateral displacement and internal force of the structure under three typical lateral loads are derived and verified by numerical method.It is studied the bending moment and shear force distribution under the action of the vertex concentrated load.By the method of orthogonal test,the sensitivity analysis found that the area of the mega column is the controllability of the lateral displacement of the structure and the width of the core tube affects the bending moment and shear force distribution ratio of the inner and outer tube.Based on the design method of stiffness principle,the concept of equivalent lateral stiffness ratio η is proposed.When η is between 3 and 4,the structure design is more economical and reasonable.Combined with project example,the stiffness degradation of the structure is analyzed by using the reduction coefficient of coupling beam stiffness.