Strength prediction of built-up radially battened columns in torsional buckling

The built-up radially battened column (RBC) has found its promising application in public buildings due to its aesthetical form and good load-bearing capacity. Like the X-shaped column, torsional buckling may be the major failure mode of the RBC under axial compression. However, current specifications lack rational design methods for the torsional buckling strength prediction of this innovative column. This paper will focus on the torsional buckling behaviour of the RBC and propose its corresponding strength design formulas. At first, the key sectional properties of the radially continuous-web tube columns (RCTC) are derived theoretically and are proven to be consistent with the numerical calculation result. Then, a finite element model (FEM) using the shell element of RCTC is established, accordingly, the elastic torsional buckling behaviour of RCTCs is investigated, and an expression for accurately estimating the elastic torsional buckling load of RCTCs is proposed. Afterward, the FEM of built-up RBCs is established to conduct the elastic buckling analysis and elastoplastic bearing capacity pre-diction. The elastic torsional buckling load of built-up RBCs is predicted by modifying the expression for RCTCs via the number of battens and the proportion of the area of battens. A key design parameter, the normalized slenderness ratio, is also obtained. Finally, the strength design recommendation of the RBCs for torsional buckling is presented on the ground of numerous elastoplastic FEM results by changing the normalized slen-derness ratio, and a limit RBCs' dimension that can prevent the built-up RBC from the torsion buckling is further proposed. These results are expected to guide the design of the RBC and promote its application in engineering.