So You Want to Use K-Factors, Do You? The Effective Length Method vs. the Direct Analysis Method [N40]

With the introduction of AISC 360-05, Specification for Structural Steel Buildings, the direct analysis method with K = 1.0 for frames in which sidesway is not prevented was introduced. To understand the significant benefit to the designer in taking K = 1.0, this presentation will discuss what is meant by a rational method of analysis as required by the 1963 Specification, will consider the K-factor alignment charts first introduced in the Commentary to the 1963 Specification, and will show comparisons between values obtained through the alignment chart and those obtained through rational methods of analysis. Results from design examples implementing the effective length method, that is K by a rational analysis, and the direct analysis method will be discussed and recommendations on selecting the appropriate method will be given.

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