Behavior of Octagonal High-Strength Steel Tubular Stub Columns

This paper investigates the behavior of octagonal high-strength steel tubular cross sections under axial compression. Experimental investigations were conducted on cross sections with three nominal dimensions fabricated from different routes of welding or combinations of cold-bending and welding. Material properties and geometric imperfections of the cross sections were measured and are reported here. A total of 18 stub column tests were carried out; load-deformation histories and failure modes of octagonal high-strength steel tubular-section stub columns are presented and discussed. Nonlinear finite-element models were validated to replicate the stub column tests and subsequently applied to carry out parametric studies for further investigating the structural performance of octagonal tubular cross sections with various slenderness values under axial compression. The results from experiments and finite-element modeling are used to evaluate the applicability of codified cross-section classification limits and various existing design methods to octagonal high-strength steel tubular cross sections under axial compression. Modifications to the cross-section classification limits and design methods are proposed to obtain more accurate predictions of cross-section classification and strengths of structures for efficient structural design.