Lacing and unsupported chord stability characteristics in short CFS built-up columns : Tests, FEA and design aspects

Built-up columns comprising of two channels in the back-to-back arrangement are the primary compression members adopted in low rise cold-formed steel (CFS) framed structures. The limited past studies on CFS built-up columns have indicated improved performance when adequately gapped chords are adopted, with no findings on laced columns (with channel chords) available in the literature. This first part of this study deals with tests on pin ended short CFS laced built-up columns, with channel chords connected using lacing plates with a single lacing arrangement. The cross-sectional aspect ratio and the lacing slenderness was controlled through transverse chord spacing and lacing thickness, respectively. The aspect ratio and lacing slenderness varied from 0.75-1.25 and 40-145, respectively. The adequacy of the limiting value for lacing slenderness recommended by Specification for Structural Steel Buildings (AISC 360-16) as 140 will also be checked. The stability characteristics of the lacing plates and the unsupported chords will be studied. The compression performance of the built-up columns will be assessed in terms of the ultimate loads, load-displacement response, failure modes and load-strain response. The second part of this study focuses on the numerical analysis, comprising validation and parametric study (lacing slenderness, chord compactness, and overall slenderness within the inelastic zone). A vast pool of data points will be generated. The last component of this study deals with determining the design strengths of the built-up columns using North American Specification and Eurocode for CFS structures for checking the accuracy of these predictions.

Learning Objectives:
Adequacy of the lacing slenderness.

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