Testing, simulation and design of cold-formed stainless steel CHS columns

Abstract

Stainless steel tubular members are employed in a range of load-bearing applications due to their strength, durability and aesthetic appeal. From the limited existing test data on stainless steel circular hollow sections (CHS) columns it has been observed that the current Eurocode 3 provisions can be unconservative in their capacity predictions. A comprehensive experimental programme has therefore been undertaken to provide benchmark data to validate numerical models and underpin the development of revised buckling curves; in total 17 austenitic, 9 duplex and 11 ferritic stainless steel CHS column buckling tests and 10 stub column tests have been carried out. Five di↵erent cross-section sizes (covering class 1 to class 4 sections) and a wide range of member slendernesses have been examined. The experiments were initially replicated using finite element (FE) simulations; the validated FE models were then used to generate 450 additional column buckling data points. On the basis of the experimental and numerical results, new design recommendations have been made for cold-formed stainless steel CHS columns and statistically validated according to EN 1990 (2005).

Numerical modelling and fire design of stainless steel hollow section columns

“…The finite element analysis package ABAQUS [9] was employed. The numerical modelling investigation involved two stages; these comprised the validation of the finite element models using the results of column tests from literature test programmes reported in [1,10,11] for SHS and RHS at elevated temperature and in [12,13] for CHS at room temperature, which is described in Section 2, and the generation of additional column flexural buckling performance data through a parametric study, which is presented in Section 3.…”

“…The key details of the elevated temperature tests on SHS and RHS columns carried out by Tondini et al [1], Ala-Outinen and Oksanen [10] and Baddoo and Gardner [11], including stainless steel grade, boundary conditions, measured column length L, applied load and critical temperature θcrit are reported in Table 1 and those for the room temperature tests on CHS columns performed by and reported in Zhao et al [12] and Buchanan et al [13] are presented in Table 2, where in addition, the measured ultimate load Nu is reported. The SHS and RHS columns tested in [1] and [10] were formed by cold-forming, where the sheet material was first made into a circular tube by cold-rolling and closed by seam-welding and then made into the required cross-section size and geometry.…”

“…For the RHS columns tested in [11], two channel sections, formed by press-braking, were welded tip-to-tip in the longitudinal direction. The CHS columns tested in [12,13] were also cold-formed, where the sheet material was cold-rolled into a circular tube and subsequently welded closed.…”

“…and press-braked stainless steel sections were employed to determine the room temperature strengths. Eqs (1) and 2 For the room temperature CHS column tests reported in [12,13], reported values from tensile coupon tests on materials cut from the cold-formed sections were used to obtain the stress-strain response of the material, which were directly used in the development of the FE models of the CHS columns.…”

“…Finally, the predicted flexural buckling resistance Nb,fi,t,Rd of a compression member at time t and experiencing a uniform temperature θ is obtained from Eqs (12) and (13), where A is the crosssectional area for the gross cross-section, Aeff is the cross-sectional area of the effective crosssection, γM,fi is the member resistance partial resistance factor, which is 1.0 as set out in [6] and all other symbols are as previously defined. grades and 0.9 for duplex (EN 1.4462) grade [20].…”