Discrete Bracing Analysis for Light-Frame Wood-Truss Compression Webs
Publication: Journal of Structural Engineering
Volume 126, Issue 9
Abstract
Light-frame wood roof trusses often require lateral bracing to reduce the effective length of compression web members for buckling purposes. Three simple analysis methods were compared in a physical test program to determine if any could adequately predict required brace strength and stiffness. A test program measured brace force and lateral deflection at midheight of 774 nominal 2 × 4 (38 × 89 mm) lumber columns of two grades and four lengths loaded in axial compression and braced with a nonlinear support. Lumber length or grade had little practical effect on the relative accuracy of the three analysis methods. Brace instability, observed in 1% of the tests, suggests the need to limit brace loads. Using 2% of the axial load to predict brace force was generally conservative but may not be appropriate, because it does not ensure sufficient brace stiffness. Two other evaluated methods, modified to achieve design conservatism, can provide a rational basis for bracing design that considers both required strength and stiffness.
Get full access to this article
View all available purchase options and get full access to this article.
References
1.
BWT-76: Bracing of wooden trusses. (1976). Truss Plate Institute, Madison, Wis.
2.
Callahan, E. E. (1993). Metal plate connected wood truss handbook, Wood Truss Council of America, Madison, Wis.
3.
Clarke, M. J., and Bridge, R. Q. ( 1993). “Bracing force and stiffness requirements to develop the design strength of columns.” Is your structure suitably braced? J. M. Ricles and D. Walsh, eds., Structural Stability Research Council, Bethlehem, Pa., 75–86.
4.
Committee on Design of Steel Building Structures of the Committee on Metals, ASCE Structural Division. (1992). “Compendium of design office problems.”J. Struct. Engrg., ASCE, 118(12), 3444–3453.
5.
Galambos, T. V. (1988). Guide to stability design criteria for metal structures, 4th Ed., Wiley, New York.
6.
Grading rules for west coast lumber. (1996). West Coast Lumber Inspection Bureau, Portland, Ore.
7.
HIB-91: Commentary and recommendations for handling, installing & bracing metal plate connected wood trusses. (1991). Truss Plate Institute, Madison, Wis.
8.
Hoyle, R. J., and Woeste, F. E. (1989). Wood technology in the design of structures, Iowa State University Press, Ames, Iowa.
9.
Kagan, H. A. (1993). “Common causes of collapse in metal plate connected wood roof trusses.”J. Perf. Constr. Fac., ASCE, 7(9), 225–234.
10.
Madsen, B. (1992). Structural behavior of timber, Timber Engineering, Ltd., N. Vancouver, B.C.
11.
McGuire, W. (1968). Steel structures, Prentice-Hall, Englewood Cliffs, N. J.
12.
Medland, I. C. (1977). “A basis for the design of column bracing.” Struct. Engr., 55(7), 301–307.
13.
Nair, R. (1988). “Simple solutions to stability problems in the design office.” Proc., 1988 Nat. Steel Constr. Conf., American Institute of Steel Construction, Chicago, 38/1–38/15.
14.
Nair, R. S. (1992). “Forces on bracing systems.” Engrg. J. Am. Inst. Steel Constr., 29(1), 45–47.
15.
National design specification for wood construction. (1997). American Forest and Paper Association, Washington, D.C.
16.
O'Connor, C. (1979). “Imperfectly braced columns and beams.” Civ. Engrg. Trans., 21(2), 69–74.
17.
Pagel, K. J. (1997). “Implementation of ANSI/TPI 1-1995—a legal perspective.” WTCA Woodworks, July, 6–7.
18.
Plaut, R. H. (1993a). “Bracing of columns with two spans.”J. Struct. Engrg., ASCE, 119(10), 2913–2931.
19.
Plaut, R. H. ( 1993b). “Bracing requirements for columns with equal or unequal spans.” Is your structure suitably braced? J. M. Ricles and D. Walsh, eds., Structural Stability Research Council, Bethlehem, Pa.
20.
Plaut, R. H., and Yang, J. G. (1993). “Lateral bracing of columns with two unequal spans.”J. Struct. Engrg., ASCE, 119(10), 2896–2912.
21.
Stalnaker, J. J., and Harris, E. C. (1989). Structural design in wood, Van Nostrand Reinhold, New York.
22.
Stanway, G. S., Chapman, J. C., and Dowling, P. J. (1992). “A simply supported imperfect column with a transverse elastic restraint at any position. Part 1: Behavior.” Proc., Inst. Civ. Engrs. Struct. Build., 94(2), 205–216.
23.
Throop, C. M. (1947). “Suggestions for safe lateral bracing design.” Engrg. News-Record, Feb. 6, 90–91.
24.
Timoshenko, S. P., and Gere, J. M. (1961). Theory of elastic stability, McGraw-Hill, New York.
25.
TPI 1-1995: National design standard for metal plate connected wood truss construction. (1995). Truss Plate Institute, Madison, Wis.
26.
Tsien, H. S. (1942). “Buckling of a column with nonlinear lateral supports.” J. Aeronaut. Sci., 9(4), 119–132.
27.
Waltz, M. E. Jr. ( 1998). “Discrete compression web bracing design for light-frame wood trusses.” MS thesis, Oregon State University, Corvallis, Ore.
28.
Winter, G. (1960). “Lateral bracing of columns and beams.” Trans. ASCE, 125, 807–845.
29.
Woeste, F. E. (1998). “Impact of permanent diagonal bracing of different MPC wood truss types.”Pract. Periodical on Struct. Des. and Constr., ASCE, 4(1), 21–23.
30.
Yura, J. A. ( 1996a). “Bracing for stability—state-of-the-art.” Bracing for stability, J. A. Yura and T. A. Helwig, eds., Structural Stability Research Council, American Institute of Steel Construction, Bethlehem, Pa.
31.
Yura, J. A. (1996b). “Winter's bracing approach revisited.” Engrg. Struct., 18(10), 821–825.
32.
Zuk, W. (1956). “Lateral bracing forces on beams and columns.”J. Engrg. Mech. Div., ASCE, 82(3), 1032-1–1032-16.
Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 126 • Issue 9 • September 2000
Pages: 1086 - 1093
History
Received: Jul 28, 1999
Published online: Sep 1, 2000
Published in print: Sep 2000
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.