Abstract

INTRODUCTION The flexural buckling of columns is a fundamental problem whose solution was found by Euler more than 200 years ago. Since then, refinements have extended the solution to the inelastic range and clarified the influence of initial deflections and residual stresses. Most of these advances were made by studying hot-rolled steel columns, which are widely used. Cold-formed sections are coming into greater and greater use, thanks to the great variety of geometries available, which make them suitable for specific needs, and the significant advances made in the last four decades in understanding the behavior of cold-formed steel and in developing simple design methods. Previous works on the behavior and strength of cold-formed members in compression have concentrated on phenomena associated with, but not specific to thin-walled structures, such as local and torsional buckling. For flexural buckling, only a few tests have been performed on cold-formed sections, and use has been made of results developed for hot-rolled sections, although cold-forming affects the mechanical properties of steel differently than hot-rolling; in particular, cold work increases the yield strength at the expense of ductility and introduces residual stresses which are completely different from the thermal residual stresses in hot-rolled sections. The need for the present study, the flexural buckling strength of cold-formed columns, is thus clear. It is, of course, impossible to investigate all types of cross-sections; only the stiffened channel and the hat sections are studied here, mainly because of their availability and many structural uses. The extension to other shapes must be done by theory. This work starts with a review of the column problem (Chapter 2) and measurements of the effects of cold-forming (Chapter 3). Next, residual stresses due to cold-forming are investigated, both theoretically (Chapter 4) and experimentally (Chapter 5). Chapter 6 develops a numerical scheme for determining column strength. Chapter 7 shows the results of stub column tests. Chapter 8 examines the effects of initial out-ot-straightness and the process of load alignment. Chapter 9 covers the procedure for testing long columns and discusses the results. Finally, the conclusions of this study and recommendations for future work are presented in Chapter 10.

Department(s)

Civil, Architectural and Environmental Engineering

Research Center/Laboratory(s)

Wei-Wen Yu Center for Cold-Formed Steel Structures

Sponsor(s)

American Iron and Steel Institute

Publisher

Unknown

Publication Date

2-1-1980

Document Version

Final Version

Comments

Draft

Document Type

Report - Technical

File Type

text

Language

English

Technical Report Number

Report No. 80-4


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