AISI-Specifications for the Design of Cold-Formed Steel Structural Members

Alternative Title

Research report RP03-1

Abstract

The “North American Specification for the Design of Cold Formed Steel Structural Members” (2001a) (herein referred to as NAS), established in 2001, governs the design of cold formed steel structural members in North America. Given in the specification are equations to predict the various failure modes of cold formed steel members in compression, tension, shear, and bending. The concern of this study was the failure mode called web crippling, which is the deformation of the web elements under concentrated compression loads. It is difficult (if not impossible) to develop an analytical design method for web crippling of cold formed steel members because of the large deformations, plasticity, variety of section geometries, and loading patterns involved with this failure mode. To simplify the design process, an empirical equation for predicting web crippling capacity is presented in the NAS. The NAS contains tables of coefficients to be used in conjunction with the design equation that account for the different section geometries, load cases, and support conditions Investigated in this study was the web crippling capacity of multi-web deck sections subjected to End One-Flange loading. There was limited data available in the published literature to support the current coefficients for multi-web decks under End One-Flange loading. Consequently, this study was initiated to derive values that are more accurate. A total of 148 tests were carried out on a range of deck profiles, bearing widths, and fastening conditions. In addition, test data from previous web crippling studies of multi-web deck sections were also considered. It was found that not all specimens from previous studies were tested in a fashion that produced acceptable results. New resistance factors and factors of safety were also developed. New coefficients were established using the data from this study and any appropriate data from previous work. Also investigated in this study was the web crippling capacity of partially-fastened deck sections and re-entrant deck sections under the same loading conditions. Partially-fastened decks sections are sections that are fastened to supports in a manner that does not meet industry standards. Re-entrant deck sections are multi-web deck sections with a web inclination greater than 90º. 77 partiallyfastened multi-web decks and 36 re-entrant decks were tested in this study. It was found that partiallyfastened deck sections, unfastened re-entrant deck sections, and fastened re-entrant deck sections all behave similarly to fully-fastened multi-web deck sections and can use the same coefficients, resistance factors, and factors of safety for design purposes. The ranges of the test specimen parameters were: 299 MPa (43.4 ksi) < Fy < 674 MPa (97.8 ksi); 1.41 < R/t < 19.9; 20.0 < N/t < 110; 20.8 < h/t < 211; and 71º< θ < 108º. These parameters are defined in Section 2.10 (page 15).

Research Center/Laboratory(s)

AISI - Specifications for the Design of Cold-Formed Steel Structural Members
Wei-Wen Yu Center for Cold-Formed Steel Structures

Sponsor(s)

American Iron and Steel Institute
University of Waterloo, Department of Civil Engineering

Publisher

American Iron and Steel Institute

Publication Date

5-1-2003

Document Version

Final Version

Rights

© American Iron and Steel Institute

Document Type

Report - Technical

File Type

text

Language

English


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