Session Start Date

8-24-2012

Session End Date

8-25-2012

Abstract

Permanent stability bracing of Cold-Formed Steel (CFS) roof/floor trusses is needed for the three major planes in a truss: Top chord, Bottom Chord and Web. Primary function of bracing is to prevent lateral instability of members as well as stiffen the overall roof/floor system. Brace force is dependent on the magnitude of applied loads and the level of out-of-planeness permitted. Traditionally, 2% of the axial compression force in a member is used as the brace (restraint) force, which is based on an out-of-plane deflection of L/200 where L is the member length. Continuous Lateral Restraint (CLR) forces are accumulated from similar members in several adjacent trusses and then transferred through Diagonal Braces (DB) to the bearings or other shear resisting elements (for example, metal decking). For chord and web members, a method to determine the forces in CLR and DB is presented using a statics based approach with varying number of braces and mode shapes for a maximum permitted out-of-planeness of L/200. For the chord members with more than two CLR's, a method for designing a Brace Collector Frame (BCF) based on the Net Lateral Restraining Force (NLRF) is presented.

Department(s)

Civil, Architectural and Environmental Engineering

Research Center/Lab(s)

Wei-Wen Yu Center for Cold-Formed Steel Structures

Meeting Name

21st International Specialty Conference on Cold-Formed Steel Structures

Publisher

Missouri University of Science and Technology

Publication Date

8-24-2012

Document Version

Final Version

Rights

© 2012 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Permanent Stability Bracing of CFS Trusses

Permanent stability bracing of Cold-Formed Steel (CFS) roof/floor trusses is needed for the three major planes in a truss: Top chord, Bottom Chord and Web. Primary function of bracing is to prevent lateral instability of members as well as stiffen the overall roof/floor system. Brace force is dependent on the magnitude of applied loads and the level of out-of-planeness permitted. Traditionally, 2% of the axial compression force in a member is used as the brace (restraint) force, which is based on an out-of-plane deflection of L/200 where L is the member length. Continuous Lateral Restraint (CLR) forces are accumulated from similar members in several adjacent trusses and then transferred through Diagonal Braces (DB) to the bearings or other shear resisting elements (for example, metal decking). For chord and web members, a method to determine the forces in CLR and DB is presented using a statics based approach with varying number of braces and mode shapes for a maximum permitted out-of-planeness of L/200. For the chord members with more than two CLR's, a method for designing a Brace Collector Frame (BCF) based on the Net Lateral Restraining Force (NLRF) is presented.