Framed tube structures are particularly suitable for tall buildings. They act primarily like cantilevered box beams and since they generally have much larger lateral dimensions than the internal shear wall cores, they are more effective in resisting the overturning moments of the lateral loads. However, due to flexural and shear flexibilities of the frame members, the basic beam bending actions of the framed tubes are complicated by the occurrence of shear lag, which could significantly affect the stress distributions in the frame panels and reduce the lateral stiffnesses of the structures. In this paper, a simple hand‐calculation method is proposed for approximate analysis of framed tube structures with the shear lag effects taken into account. This method is suitable for quick evaluations during the preliminary design stage and can provide a better understanding of the effects of various parameters on the overall structural behavior. Numerical examples are given to demonstrate the ease of application an...

Simple Method for Approximate Analysis of Framed Tube Structures

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A simple mathematical model for approximate analysis of tall buildings

A framed-tube system with multiple internal tubes is analyzed using an orthotropic box beam analogy approach in which each tube is individually modeled by a box beam that accounts for the flexural ...

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Simple Analysis of Framed-Tube Structures with Multiple Internal Tubes

A high-rise diagrid tube structure is a new type of building structural system that can provide greater lateral stiffness . Simplified calculation methods for diagrid tube structures have been studied by scholars in recent years, but the shear lag effects in such structures have not been reviewed. The shear lag effect will affect the lateral stiffness and stress distribution of a tube structure, so it is necessary to propose a simplified calculation method that can consider the shear lag effect of diagrid tube structures. This paper adopts the principle of stiffness equivalence to equate a high-rise diagrid tube structure to an elastic orthotropic membrane, constructs the stress function considering the shear lag effect under the action of typical horizontal loads, and obtains the stress function through the principle of energy variation. A simplified calculation method is achieved; calculation formulas for the components internal forces and structural displacements are deduced and compared with a detailed finite element program calculation to verify the method. Further, through the simplified calculation method proposed in this paper, two key issues (angle optimization of diagonal columns and evaluation of the shear lag effect at any aspect ratio) are solved in the preliminary design of this kind of structure. Results of this paper can provide a theoretical reference for the preliminary design of a diagrid tube structure. Under the basic condition that only the aspect ratio of the structure is known, the optimal angle of diagonal column can be determined, and the shear lag effect of the diagrid structure can be quickly estimated by the proposed simplified method.

Simplified calculation of shear lag effect for high-rise diagrid tube structures

SUMMARY

In this study, effects of applying higher order axial displacement distribution to solve a continuum model for static analysis of the combined system of framed tube, shear core and outrigger–belt truss system in high-rise buildings are investigated. Framed tube system is modeled using an orthotropic box beam analogy approach and the interaction between shear core and outrigger–belt truss system on framed tube is modeled with rotating spring placed at outrigger–belt truss location. The axial displacement distributions in web and flange panels along structure's height are proposed to be fifth-order and fourth-order polynomials, respectively. Analytic analyses are carried out on the basis of the principle of minimum potential energy. A detailed work is carried out through two numerical examples and the accuracy of proposed approximation functions is compared with previous work and finite element analysis. Results demonstrate that the proposed parametric stress distribution and displacement functions are more accurate than previously proposed functions in comparison with the finite element solution. Copyright © 2012 John Wiley & Sons, Ltd.

A.H. Khan

Papers

A simple method of analysis for deflection and stresses in wall-frame structures