Session Start Date

11-7-2018

Session End Date

11-8-2018

Abstract

A procedure is presented to calculate the local and distortional flexural buckling strength of continuous span purlins with paired torsion braces using the Direct Strength Method. Displacement compatibility is utilized to determine the forces interacting between the purlin, the flexible diaphragm and the torsion braces. The biaxial bending and torsion effects caused by this interaction are superimposed, and the actual distribution of stresses within the cross section are calculated at critical locations along the span. With this distribution of stresses, a finite strip buckling analysis is performed to determine the local and distortional buckling strength. In current design practice, results from a simple span Base Test are extrapolated to multi-span systems using a constrained bending stress distribution. In previous work, a variation of the presented method was compared to simple span base test results with good correlation. In this paper, the simple span stresses are compared to the stresses of continuous span systems. Significant, although typically conservative differences in the stress distributions and, as a result the predicted flexural strength, are observed in the comparison between simple span and multi-span systems. Additionally, significant changes in the distribution of stresses are observed as roof slope effects are considered. Increases in the flexural strength with increasing roof slope are reported and compared to the strength predicted by the current base test method.

Author

Michael Seek

Department(s)

Civil, Architectural and Environmental Engineering

Meeting Name

Wei-Wen Yu International Specialty Conference on Cold-Formed Steel Structures 2018

Publisher

Missouri University of Science and Technology

Publication Date

11-7-2018

Document Version

Final Version

Rights

© 2018 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Nov 7th, 12:00 AM Nov 8th, 12:00 AM

Flexural Strength of Continuous-Span Z-Purlins with Paired Torsion Braces using the Direct Strength Method

A procedure is presented to calculate the local and distortional flexural buckling strength of continuous span purlins with paired torsion braces using the Direct Strength Method. Displacement compatibility is utilized to determine the forces interacting between the purlin, the flexible diaphragm and the torsion braces. The biaxial bending and torsion effects caused by this interaction are superimposed, and the actual distribution of stresses within the cross section are calculated at critical locations along the span. With this distribution of stresses, a finite strip buckling analysis is performed to determine the local and distortional buckling strength. In current design practice, results from a simple span Base Test are extrapolated to multi-span systems using a constrained bending stress distribution. In previous work, a variation of the presented method was compared to simple span base test results with good correlation. In this paper, the simple span stresses are compared to the stresses of continuous span systems. Significant, although typically conservative differences in the stress distributions and, as a result the predicted flexural strength, are observed in the comparison between simple span and multi-span systems. Additionally, significant changes in the distribution of stresses are observed as roof slope effects are considered. Increases in the flexural strength with increasing roof slope are reported and compared to the strength predicted by the current base test method.