Doubly Symmetric Tube Structures. I: Static Analysis

This paper presents a simplified analytical method usable in preliminary stages of the design to doubly symmetric tube structures in high‐rise structures by means of an extended rod theory including the bending, transverse shear deformation, shear lag and torsion. The discontinuous variation of sectional stiffness due to frame members and attached braces is expressed as a continuous function by means of the extended Dirac function. The deflection, shear lag, and torsional angle of the variable tube structures with braces are given in closed‐form solutions. The exactness of the closed‐form solutions is established from numerical results for a doubly symmetric and variable frame tube with braces, in which the results obtained from the proposed solutions are compared with results obtained from the three‐dimensional frame analysis using FEM code NASTRAN.