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Resistance of cold-formed high strength steel circular and polygonal sections: Part 2: Numerical investigations
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Fire Engineering.
Delft University of Technology.ORCID iD: 0000-0003-4791-2341
University of Coimbra, ISISE, Department of Civil Engineering, University of Coimbra.
Virginia Polytechnic Institute and State University, Universidade de Coimbra , ISISE, Department of Civil Engineering, University of Coimbra.
Number of Authors: 42016 (English)In: Journal of constructional steel research, ISSN 0143-974X, E-ISSN 1873-5983, Vol. 125, p. 227-238Article in journal (Refereed) Published
Abstract [en]

This paper is the second part of the study on the cold-formed high strength steel circular and polygonal sections intended to be used in tubular wind towers. Results from 32 numerical finite element analysis (FEA) models were compared with and calibrated against results of the tests on 32 corresponding specimens. The FEA results agreed well with the experimental results in terms of resistances and load-displacement curves. Further investigations on the numerical models were performed. Yield stress used in the FEA significantly affected the resistances of the numerical models. Using 0.2% proof stress leaded to higher resistance than the experimental results. Corners significantly influenced buckling behaviour in the polygonal section models. Analyses of an oval opening in the tubular specimens showed that peak stresses around the opening were considerably higher in the polygonal section models than in the circular section models. Finally, investigation of sensitivity to geometrical imperfections indicated that failure modes of numerical models with geometrical imperfections according to EC3 significantly differed from those of tested specimens and numerical models with geometrical imperfections obtained from the 3D scans.

Place, publisher, year, edition, pages
2016. Vol. 125, p. 227-238
National Category
Building Technologies
Research subject
Steel Structures
Identifiers
URN: urn:nbn:se:ltu:diva-7640DOI: 10.1016/j.jcsr.2016.06.014ISI: 000381834200017Scopus ID: 2-s2.0-84976871845Local ID: 60a8f640-4371-4b15-a819-88e3073103a4OAI: oai:DiVA.org:ltu-7640DiVA, id: diva2:980530
Note

Validerad; 2016; Nivå 2; 20160705 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
In thesis
1. Resistance of cold-formed high strength steel sections: Effect of cold-formed angle
Open this publication in new window or tab >>Resistance of cold-formed high strength steel sections: Effect of cold-formed angle
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Cold-formed steel members are increasingly used in industrial and civil construction. Their use allows optimised member cross sections and shapes, thereby reducing the amount of steel used as well as the weight of the structures and, consequently, reducing harmful effects on the environment. Cold-formed members are manufactured using various methods such as cold rolling or press braking. In the cold rolling method, the cold-formed member is made by passing a flat steel sheet through a series of deformation stages. In the press braking method, the cold-formed member is produced by bending a flat steel sheet along its length. Cold-formed steel circular and polygonal sections have been used for wind turbine tubular towers. In order to harness the maximum amount of the wind's kinetic energy, the height of wind turbine tubular towers has significantly increased over the last few decades. Using high strength steel material has proven to be a feasible solution to the problem of the increasing height of wind turbine towers. The use of high strength steel material for cold-formed members significantly improves their properties. It enables thinner, longer and stronger structures. Moreover, the quantity of steel material required for building cold-formed steel structures is considerably reduced, producing a beneficial effect on the environment.

This thesis describes experimental and numerical investigations of cold-formed high strength steel sections and the effects of cold-formed angles on their properties. The effect of cold-formed angles on the properties of high strength steel was studied using tensile coupon tests. Coupon specimens with different cold-formed angles and different thicknesses were considered. Experimental results revealed that the cold-formed angle has a significant effect on the material properties. Furthermore, the cold-formed angle dependencies of the yield and tensile strengths were determined, and the strengths obtained with/without considering the influence of the cold-formed angle were compared. The yield and tensile strengths both decreased with increasing coldformed angle. The behaviour of cold-formed high strength steel angles was also investigated. Thirty-six specimens with different cold-formed angles (90°, 100°, 120°, 140°, 160°, and 170°) and different thicknesses (4 mm and 6 mm) were used for the investigation. Test results indicated that the resistance of the cold-formed angles significantly decreases, by 84%, with increasing coldformed angles from 90° to 170° (reducing influence of cold-forming). Moreover, a cold-formed angle significantly affects the failure modes of the angles. Experimental and numerical studies of cold-formed high strength steel circular and polygonal sections were carried out. A total of 32 cold-formed high strength steel circular and polygonal specimens, with and without openings, were tested under uniaxial compression. Initial geometric imperfections of the specimens were detected by using a 3D laser scanning method. Finite element analysis (FEA) models were compared with, and calibrated against, test results. The FEA results agreed well with the experimental results.

Place, publisher, year, edition, pages
Luleå University of Technology, 2019
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Civil Engineering
Research subject
Steel Structures
Identifiers
urn:nbn:se:ltu:diva-64936 (URN)978-91-7583-931-8 (ISBN)978-91-7583-932-5 (ISBN)
Public defence
2019-11-13, F1031, Luleå University of Technology, 10:00 (English)
Opponent
Supervisors
Available from: 2017-08-11 Created: 2017-08-02 Last updated: 2019-10-23Bibliographically approved

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