Dynamics-Based Analytical Correlation between Flexure–Shear Coupled Model and Frame–Tube–Outrigger Model for Frame Core–Tube Structural Systems

Abstract

To establish a physically direct link between the subsystem-level stiffness demand (i.e., the external frame system, internal core tube, link beam system, and outrigger-belt system) and that at the global system level of frame core-tube structural systems that have been commonly used in super high-rise buildings, this paper examines the analytical correlation of the dynamic characteristics between the modified flexure-shear coupled model (FSM-MS) and modified frame-tube-outrigger model (MFTOM) proposed previously. The MFTOM is developed with the appropriate distribution functions of linear density and subsystem stiffness in the frame-core tube system, and its approximate vibration periods are analytically determined by the rationally assumed mode shape and derived approximate mode shape derivative and curvature. From the perspective of the energy balance of the free vibration, the frequency amplification factor induced by outriggers is formulated. The effectiveness of the correlation established by the first two order vibration periods is systematically demonstrated from a series of cases, from the aspects of vibration periods and inter-story drift ratios. The results of the parameter analysis indicate that the influence of the outrigger on the structural shear-flexural stiffness ratio is mainly realized by the constraint on the flexural deformation of the core tube and the amplification of the axial deformation of the column. The proposed correlation not only provides a reliable theoretical basis for distributing the structural lateral stiffness to the subsystem stiffness in the preliminary design, but can also be used as a practical tool to adjust the overall lateral deformation shape of the frame-core tube system.