A SIMPLIFIED ANALYSIS OF DOUBLY SYMMETRICAL TUBE STRUCTURES

This paper discusses the exactness of a simplified analytical method proposed by Takabatake et al. (1993) to use in preliminary stages of the design to doubly symmetric single and double frame-tubes in high-rise structures. The simplified method is formulated by replacing the tube with an equivalent rod, including the effect of the bending, transverse shear deformation, shear-lag and torsion. The discontinuous variation of sectional stiffness of tube structures, due to the variation of frame members and attached braces, is expressed as a continuous function by means of the extended Dirac function. The exactness of the closed-form solutions proposed here for the deflection, shear-lag, and torsional angle of variable tube structures with braces is established from static and dynamic numerical results for doubly symmetric single and double frame-tubes with braces, in which the results obtained from the proposed solutions are compared with results obtained from three-dimensional frame analysis using the FEM codes NASTRAN and DEMOS.