Discrete bracing analysis for light-frame wood-truss compression webs

Citation
Me. Waltz et al., Discrete bracing analysis for light-frame wood-truss compression webs, J STRUC ENG, 126(9), 2000, pp. 1086-1093
Citations number
31
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Civil Engineering
Journal title
JOURNAL OF STRUCTURAL ENGINEERING-ASCE
ISSN journal
0733-9445 → ACNP
Volume
126
Issue
9
Year of publication
2000
Pages
1086 - 1093
Database
ISI
SICI code
0733-9445(200009)126:9<1086:DBAFLW>2.0.ZU;2-K
Abstract
Light-frame wood roof trusses often require lateral bracing to reduce the e ffective length of compression web members for buckling purposes. Three sim ple analysis methods were compared in a physical test program to determine if any could adequately predict required brace strength and stiffness. A te st program measured brace force and lateral deflection at midheight of 774 nominal 2 x 4 (38 x 89 mm) lumber columns of two grades and four lengths lo aded in axial compression and braced with a nonlinear support. Lumber lengt h or grade had little practical effect on the relative accuracy of the thre e analysis methods. Brace instability, observed in 1% of the tests, suggest s the need to limit brace loads. Using 2% of the axial load to predict brac e force was generally conservative but may not be appropriate, because it d oes not ensure sufficient brace stiffness. Two other evaluated methods, mod ified to achieve design conservatism, can provide a rational basis for brac ing design that considers both required strength and stiffness.