CCFSS Library (1939 - present)

Abstract

Cold-forming may cause significant increases in tensile and in compressive yield strength in both the corner and flat elements of light-gage cold-formed steel members. The cumulative effects may raise the yield strength to as reuch as 70% above the virgin yield strength of the as-rolled sheet steel. The yield strength of corners is always considerably higher than that of any other portion of a cold-formed member because of the large plastic deformations which take place in the corners. Thus compact members with a large ratio of corner area to cross sectional area will have the largest increases in yield strength. However, in members with a relatively low ratio of corner area to total cross sectional area the total contribution to the increased yield strength of the member may be larger in the flats than in the corners. Extensive experimental investigations were conducted to study the mechanical properties of full sections, of corner and flat elements from cold-formed sections, and of the virgin materials from which the sections were fabricated. A method is presented by which the full section tensile yield strength of light-gage members may be predicted from the results of simple tensile coupon tests rather than of full section tests. This method includes, an equation for the prediction of tensile corner yield strength which is based on basic material properties and on concepts from the theory of plasticity. An empirical equation relating plastic stresses and strains was found to be valid for all nine sheet steel materials tested. The constants in this equation are related to the tensile yield and ultimate strengths of the virgin sheet and are used in developing the corner yield strength equation. The inelastic buckling behavior of two different types of cross sections of axially loaded pin-ended columns was also investigated analytically and experimentally. These column sections were fabricated by connecting two singly symmetrical sections to form doubly symmetrical sections. Results of these tests are found to correlate well with theoretical column curves based on a modified form of the tangent modulus equation for inelastic column buckling.

Department(s)

Civil, Architectural and Environmental Engineering

Sponsor(s)

American Iron and Steel Institute

Research Center/Lab(s)

Wei-Wen Yu Center for Cold-Formed Steel Structures

Publication Date

01 Jun 1965

Document Version

Final Version

Comments

Sixth Progress Report

Document Type

Technical Report

File Type

text

Language(s)

English

Technical Report Number

Report No. 318

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