Behaviour of tubular steel members under cyclic axial loading

Abstract

This paper examines the cyclic performance of axially-loaded tubular members used as bracing elements to provide lateral seismic resistance in steel framed structures. An experimental study into the response of members with square and rectangular hollow sections, made from cold-formed steel, is described. Three cross-sectional geometries were employed to represent a range of local and overall slenderness. Fifteen specimens, with normalised slendernesses between 0.4 and 3.2, were tested under cyclic axial displacements of increasing amplitude. In addition, twenty-one short specimens were tested under displacement-controlled monotonic tension loading, focusing primarily on the relationship between the tensile resistance of the material and that of the cross-section.Based on the results obtained in both sets of tests, and with due consideration of existing design provisions, the paper assesses the influence of section and member properties on the structural parameters that are most important for seismic design. These include the tensile capacity, initial and post-buckling compressive resistance, ductility capacity, energy dissipation, and mid-length lateral deformations of bracing members.

Cyclic testing and numerical modelling of carbon steel and stainless steel tubular bracing members

“…These cracks reduce the rotational stiffness at the ends of the specimens and increase their effective length, which lessens the rotation at the mid-length. The discrepancy between the results of Goggins et al [9] and the numerical predictions may be due to the assumptions that had to be made on the material properties.A crucial criterion for accurate prediction of fracture is reproducing the strain distribution correctly in the FE models. The FE and experimental strain measurements at various stages of the cyclic axial test on Specimen 60×60×3×2850-SS-CF are presented in Figs 23(a)-(c).…”

“…However, the validity of this prediction method is limited to bracing members in inverted V braced frames. Further developments [7][8][9] in the prediction of fracture life of brace members have utilised this basic proposed equation and generalised the applicability to bracing members in other concentrically braced frame configurations.A more general relationship was established following a comprehensive survey of the experimental cyclic behaviour of steel bracing members conducted by Tremblay [7], in which buckling resistance, post-buckling resistance in compression, tensile resistance, fracture life and a number of other properties from about 50 members were assessed. Shaback and Brown [8] carried out tests on square hollow section bracing members and calibrated a more sophisticated expression of fracture life, defined as Revised Manuscript Click here to view linked References 2 the weighted sum of normalised compressive and tensile deformation, in terms of global slenderness, local slenderness, aspect ratio of the cross-section and material yield strength.…”

“…These discrepancies are attributed to the limited number of parameters (four) in the material model which can lead to inaccuracies in fully capturing the precise material response [10]. Three extra test results from Goggins et al [9] and Walpole [32] have also been employed to verify the applicability of the current models to other specimens and loading regimes, as discussed below.A comparison between the number of cycles to failure and predictions from the FE models is presented in Table 4. The agreement between test and FE results is good with only a few exceptions which may be due to the premature cracking in the weld regions.…”

“…The end connection details and loading history were the same as those employed in present study. From Walpole's study [32], the test result for a cold-formed specimen with fixed end conditions has examined in the current study, while results for other specimens with pinned end are not considered.Comparison with these additional experiments [9,32], allows the applicability of the equations to more materials and over a larger range of slenderness to be assessed.A cumulative measure of ductility takes into account the characteristics of the loading history prior to failure. Shaback and Brown define the accumulated fracture ductility ( f ) as the weighted sum of normalised compressive ( 1 ) and tensile deformation ( 2 ) [8]:…”

The Analysis of Bearing Capacity of Axially Compressed Cold Formed The Analysis of Bearing Capacity of Axially Compressed Cold Formed Steel Members

“…Goggins et al [14] investigated columns with square and rectangular cross-section. Obtained results (Table 4) shows that that American, AS /NSZ and European codes are conservative for slender columns of hollow square cross-section, except for the column lengths from 500 to 3000mm SHS.…”