Torsional Strength of Thick-Walled Aluminum Tubes ^†

An experimental study of closed hollow sections subjected to torsional loading was conducted. The aim was to examine the torsional behavior of thick-walled 6061-T6 aluminum alloy tubes. The test plan included three sets of circular and rectangular tubes, each with six specimens for a total of 36 torsion tests. Experimental data were used to estimate torsional stiffness, and both first-yield and full plastic-yield strengths. Experimental estimates were compared with theoretical predictions, as well as with values computed using the Aluminum Association’s Specification for Aluminum Structures (SAS) design rules. The SAS provisions were found to be overly conservative for thick-walled circular tubes, while fairly close agreement between SAS’s shear modulus (C) and the torsional plastic section modulus (Z_T) resulted in more accurate results for thick-walled rectangular tubes.