Bearing Capacity in Long-Span Tubular Truss Chords
Publication: Journal of Structural Engineering
Volume 133, Issue 3
Abstract
Existing design specifications used in the United States and abroad do not address the limit state of bearing failure that may govern in the design of tubular truss chords at the supports. The lack of treatment of this limit state seems to represent an unsatisfactory situation given the fact that very large concentrated reaction forces are often applied transversely to the ends of chord members with slender circular cross sections; long-span overhead highway sign trusses are but one example of an affected application. The bearing failure limit state is manifest as a coupled failure mechanism, consisting of a plastic collapse of the chord end and local plastification of the chord wall. In order to better understand this limit state, two full-scale experimental tests are conducted at the University of Pittsburgh as part of the current research. The specimens considered are proportioned to be representative of the bearing region of an overhead sign structure that failed in the limit state under investigation. These tests yield important information regarding the manifestation of the bearing limit state and also afford an opportunity to verify finite element modeling techniques for use in a parametric study. The parametric study reveals that the bearing capacity is influenced by many factors including the geometry of the bearing connection, the adjacent intermediate truss member, the nature of loading, and the material properties. Using regression analysis on the parametric study results and concepts from the yield line method for analyzing collapse mechanisms, general equations for predicting the bearing capacity are developed.
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Acknowledgments
Financial support for this project was provided by the Pennsylvania Department of Transportation (PennDOT). The views and findings reported herein are solely those of the writers and not necessarily those of PennDOT.
References
AASHTO. (2001). Standard specifications for structural supports for highway signs, luminaires and traffic signals, 4th Ed., Washington, D.C.
AISC. (2000). Load and resistance factor design specification for steel hollow structural sections, Chicago.
American Welding Society (AWS). (2004). D1.1 structural welding code—Steel, 19th Ed., Miami.
Boyle, R., and Earls, C. J. (2004). “Full-scale testing of tri-chord sign structure connections.” Rep. No. CE/ST 28, Dept. of Civil and Environmental Engineering, Univ. of Pittsburgh, Pittsburgh.
Commonwealth of Pennsylvania Department of Transportation (Penndot). (2003a). “Overhead sign structures—2-post and 4-post tri-chord truss spans from 18,288 to 73,152 (60’ to 240’) notes and design criteria.” Standard drawings for bridge construction—BC 744-M, Harrisburg, Pa.
Commonwealth of Pennsylvania Department of Transportation (Penndot). (2003b). “Overhead sign structures—2-post and 4-post tri-chord truss spans from 18,288 to 73,152 (60’ to 240’) notes and design criteria.” Standard drawings for bridge design—BD 644-M, Harrisburg, Pa.
Hibbitt, Karlsson & Sorensen, Inc. (HKS). (2003). ABAQUS theory manual, Pawtucket, R.I.
International Institute of Welding (IIW). (1989). “Design recommendations for hollow section joints—predominantly statically loaded.” IIW Document No. XV-701-89, 2nd Ed., IIW Subcommission XV-E, Helsinki, Finland.
Kosteski, N., and Packer, J. A. (2003). “Longitudinal plate and through plate-to-hollow structural section welded connections.” J. Struct. Eng., 129(4), 478–486.
Kozy, B. (2004). “Chord bearing capacity in long-span tubular trusses.” Ph.D. dissertation, Dept. of Civil and Environmental Engineering, Univ. of Pittsburgh, Pittsburgh.
Kozy, B., Boyle, R., and Earls, C. J. (2006). “Chord bearing capacity in long-span tubular trusses.” Steel Compos. Struct., 6(2), 103–122.
Kozy, B., and Earls, C. J. (2005). “Finite element modeling of tubular truss bearings.” Steel Compos. Struct., 5(1), 49-70.
Kurobane, K. (1981). “New developments and practices in tubular joint design.” IIW Doc XV-488-81, Dept. of Architecture, Kumamoto Univ., Kumamoto, Japan.
Kurobane, K., Makino, Y., and Mitsui, Y. (1976). “Ultimate strength formulae for simple tubular joints.” IIW Document No. XV-385-76, Dept. of Architecture, Kumamoto Univ., Kumamoto, Japan.
Li, Y., and Earls, C. J. (2002). “Design recommendations for the proportioning and detailing of long-span tri-chord sign structures. Phase I.” Rep. No. CE/ST 24, Dept. of Civil and Environmental Engineering, Univ. of Pittsburgh, Pittsburgh.
Marshall, P. W. (1992). Design of welded tubular connections—Basis and use of AWS Code Provisions, Elsevier, Amsterdam, The Netherlands.
Packer, J. A., and Henderson, J. E. (1997). Hollow structural section connections and trusses, 2nd Ed., Design Guide, Canadian Institute of Steel Construction, Willowdale, Ont., Canada.
Soh, C. K., Chan, T. K., and Yu, S. K. (2000). “Limit analysis of ultimate strength of tubular X-joints.” J. Struct. Eng., 126(7), 790–797.
Stamenkovic, A., and Sparrow, K. (1983). “Load interaction in T-joints of steel circular hollow sections.” J. Struct. Eng., 109(9), 2192–2204.
Toma, S., and Chen, W. F. (1979). “Analysis of fabricated tubular columns.” J. Struct. Div., 105(11), 2343–2366.
Wardenier, J. (1982). Hollow section joints, Delft University Press, Delft, The Netherlands.
Wardenier, J., Kurobane, Y., Packer, J. A., Dutta, D., and Yeomans, N. (1991). Design guide for circular hollow section (CHS) joints under predominantly static loading, CIDECT, ed., Verlag TUV Rheinland GmbH, Koln, Germany.
Yura, J. A., Edwards, I., and Zettlemoyer, N. (1981). “Ultimate capacity of circular tubular joints.” J. Struct. Div., 107(10), 1965–1984.
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© 2007 ASCE.
History
Received: Nov 17, 2005
Accepted: Aug 11, 2006
Published online: Mar 1, 2007
Published in print: Mar 2007
Notes
Note. Associate Editor: James S. Davidson
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