Lateral Buckling Strengths of Steel Angle Section Beams
Publication: Journal of Structural Engineering
Volume 129, Issue 6
Abstract
The design of unbraced steel angle section beams against biaxial bending and torsion requires the ability to predict their lateral buckling strengths when bent about the major principal axis. Present design code formulations of lateral buckling strength are based on research on doubly symmetric I-section beams, and may be inappropriate for monosymmetric and asymmetric angle section beams. This paper presents close approximations for the elastic lateral buckling moments of equal and unequal angle section beams loaded by uniformly distributed loads which act at or away from the shear center. Small and large twist rotation elastic analyses of angle section beams with initial twist rotations are used with interaction equations for the biaxial bending section moment capacities to investigate present design code formulations for lateral buckling strength. It is found that these code formulations are unnecessarily conservative, especially at high slendernesses, where the moment capacities predicted by them may be less than the minor axis section capacity instead of greater. An improved formulation is proposed which is simpler and more economic than the present formulations. The use of the elastic lateral buckling approximations in the improved design moment capacity formulation is demonstrated in a worked example.
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References
Australian Institute of Steel Construction (AISC). (1999). Design capacity tables for structural steel-Volume 1: Open sections, 3rd Ed., Australian Institute of Steel Construction, Sydney, Australia.
American Institute of Steel Construction (AISC). (2000a). Specification for load and resistance factor design of single-angle members, American Institute of Steel Construction, Chicago.
American Institute of Steel Construction (AISC). (2000b). Commentary on the specification for load and resistance factor design of single-angle members, American Institute of Steel Construction, Chicago.
Anderson, J. M., and Trahair, N. S.(1972). “Stability of monosymmetric beams and cantilevers.” J. Struct. Div. ASCE, 98(1), 269–286.
British Standards Institution (BSI). (2000). BS5950 Structural use of steelwork in building. Part 1:2000. Code of practice for design in simple and continuous construction: Hot rolled sections, British Standards Institution, London.
Column Research Committee of Japan (CRCJ). (1971). Handbook of structural stability, Corona, Tokyo.
Earls, C. J.(1999). “On single angle major axis flexure.” J. Constr. Steel Res., 51(2), 81–97.
Earls, C. J.(2001a). “Geometric axis compactness criteria for equal leg angles: Horizontal leg compression.” J. Constr. Steel Res., 57(4), 351–373.
Earls, C. J.(2001b). “Single angle geometric axis flexural compactness criteria: Horizontal leg tension.” J. Struct. Eng., 127(6), 616–624.
Earls, C. J.(2001c). “Single angle geometric axis flexure. I: Background and model verification.” J. Constr. Steel Res., 57, 602–622.
Earls, C. J.(2001d). “Single angle geometric axis flexure. II: Design recommendations.” J. Constr. Steel Res., 57, 623–646.
Earls, C. J.(2001e). “Compactness and bracing recommendations for equal leg single angle beams.” Am. Inst. Steel Const. Eng. J., 38(4), 204–217.
Earls, C. J., and Galambos, T. V.(1997). “Design recommendations for single angle flexural members.” J. Constr. Steel Res., 43(1–3), 65–85.
Earls, C. J., and Galambos, T. V.(1998). “Practical compactness and bracing provisions for the design of single angle beams.” Am. Inst. Steel Const. Eng. J., 35(1), 19–25.
Farwell, C. R., and Galambos, T. V.(1969). “Non-uniform torsion of steel beams in inelastic range.” J. Struct. Div. ASCE, 95(12), 2813–2829.
Goh, C. C., Dayawansa, P. H., and Bennetts, I. D.(1991). “Design of angles to AS4100-1990.” Steel Construction, Australian Institute of Steel Construction, 25(2), 2–14.
Leigh, J. M., and Lay, M. G. (1969). “The design of laterally unsupported angles.” Rep. MRL 22/1, BHP Melbourne Research Laboratories, Clayton, Australia.
Leigh, J. M., and Lay, M. G. (1970a). “Laterally unsupported angles with equal and unequal legs.” Rep. MRL 22/2, BHP Melbourne Research Laboratories, Clayton, Australia.
Leigh, J. M., and Lay, M. G. (1970b). “Safe load tables for laterally unsupported angles.” Rep. MRL 22/3, BHP Melbourne Research Laboratories, Clayton, Australia.
Papangelis, J. P., and Hancock, G. J. (1997). THIN-WALL-Cross-section analysis and finite strip buckling analysis of thin-walled structures, Centre for Advanced Structural Engineering, Univ. of Sydney, Sydney, Australia.
Papangelis, J. P., Hancock, G. J., and Trahair, N. S. (1997). PRFELB-Finite element flexural-torsional buckling analysis of plane frames, Centre for Advanced Structural Engineering, Univ. of Sydney, Sydney, Australia.
Papangelis, J. P., Trahair, N. S., and Hancock, G. J.(1998). “Elastic flexural-torsional buckling of structures by computer.” Comput. Struct., 68, 125–137.
Pi, Y. L., and Trahair, N. S.(1995). “Inelastic torsion of steel I-beams.” J. Struct. Eng., 121(4), 609–620.
Standards Australia (SA). (1998). AS 4100-1998 Steel structures, Standards Australia, Sydney, Australia.
Thomas, B. F., and Leigh, J. M. (1970). “The behaviour of laterally unsupported angles.” Rep. MRL 22/4, BHP Melbourne Research Laboratories, Clayton, Australia.
Timoshenko, S. P., and Gere, J. M. (1961). Theory of elastic stability, McGraw-Hill, New York.
Trahair, N. S. (1993). Flexural-torsional buckling of structures, E & FN Spon, London.
Trahair, N. S. (1997). “Multiple design curves for beam lateral buckling” Proc., 5th Int. Colloquium on Stability and Ductility of Steel Structures, Nagoya, 33–44.
Trahair, N. S.(2002a). “Moment capacities of steel angle sections.” J. Struct. Eng., 128(11), 1387–1393.
Trahair, N. S.(2002b). “Bearing, shear, and torsion capacities of steel angle sections.” J. Struct. Eng., 128(11), 1394–1398.
Trahair, N. S., and Bradford, M. A. (1998). The behaviour and design of steel structures to AS4100, 3rd Australian Ed., E & FN Spon, London.
Trahair, N. S., Bradford, M. A., and Nethercot, D. A. (2001). The behaviour and design of steel structures to BS5950, 3rd British Ed., E & FN Spon, London.
Wang, C. M., and Kitipornchai, S.(1986). “Buckling capacities of monosymmetric I-Beams.” J. Struct. Eng., 112(11), 2373–2391.
Woolcock, S. T., and Trahair, N. S.(1974). “Post-buckling behaviour of determinate beams.” J. Eng. Mech. Div., Am. Soc. Civ. Eng., 100(2), 151–171.
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Information
Published In
Journal of Structural Engineering
Volume 129 • Issue 6 • June 2003
Pages: 784 - 791
Copyright
Copyright © 2003 American Society of Civil Engineers.
History
Received: Apr 16, 2002
Accepted: Jun 13, 2002
Published online: May 15, 2003
Published in print: Jun 2003
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