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Prepared by the Task Committee on Effective Length of the Technical Committee on Load and Resistance Factor Design of the Technical Division of the Structural Engineering Institute of ASCE.
This report examines several contemporary techniques for assessing column stability in the design of steel frame structures. It provides an understanding of the strengths, limitations, and assumptions with respect to column and frame stability made in Load and Resistance Factor Design Specification for Structural Steel Buildings, (LRFD) Second Edition (1993), published by the American Institute of Steel Construction (AISC).
This report focuses on three techniques for stability design. Two approaches use effective length factors and are specifically outlined in the Commentary of the AISC specifications. The third method involves the use of a notional load approach for stability design (with the use of an effective length factor equal to one for all columns in the frame). Even though notional load approaches are not mentioned in the AISC specifications, this technique is commonly used in some form within several other design standards throughout much of the rest of the world.
Examples illustrate the procedures for both common and unusual conditions encountered in practice. This document is applicable to both unbraced and braced frames having either fully restrained or partially restrained connections. In addition, even though most of the discussions pertain equally to either AISC Allowable Stress Design or LRFD practice, all discussions in this report are framed within the context of the more current LRFD specification. A practical introduction to this material is provided through the discussions of the assumptions, advantages, and disadvantages of each of the methods and through step-by-step examples. The more detailed discussions and derivations provide a reference regarding some of the more complex issues involved with design for stability.