Truck Moment Range from Single Concentrated Load
Publication: Journal of Structural Engineering
Volume 117, Issue 10
Abstract
Recently recommended guidelines for fatigue design and evaluation of steel bridges employ a truck with an increased spacing between back axles, compared to the standard truck used for strength design. Separate structural analyses must be performed for the fatigue truck because the change in axle spacing may not be accounted for by applying a linear correction factor to the results obtained for the strength‐design truck. The moment range caused by the fatigue truck may be determined very conveniently, however, from basic bridge design aids, and the use of customized bridge‐analysis software is not required. A series of coefficients is presented for symmetrical, constant‐EI bridges that relate the moment range caused by the fatigue truck to the maximum moment produced by the truck resultant. These coefficients enable one to perform a simple analysis involving the single placement of an isolated concentrated load to obtain the moment range, rather than more extensive analyses that require several trial placements of a three‐axled vehicle. Extremely quick checks may be conducted for preliminary design purposes, or relatively accurate results may be obtained with simple linear interpolation. Accuracy from the coefficients ranges from less than 1% below the correct value to a maximum of approximately 17% above the true range. Several examples are presented to illustrate the application of the procedure.
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References
1.
Albrecht, P. (1986). “Review of fatigue design methods for highway bridges.” Department of Civil Engineering Report, University of Maryland, College Park, Md.
2.
Guide specifications for fatigue evaluation of existing steel bridges. (1990). American Association of State Highway and Transportation Officials, Washington, D.C.
3.
Moments, shears and reactions for continuous highway bridges. (1966). American Institute of Steel Construction, Chicago, Ill.
4.
Moses, F., Schilling, C. G., and Raju, K. S. (1987). “Fatigue evaluation procedures for steel bridges.” NCHRP Report 299, Transportation Research Board, Washington, D.C.
5.
Standard specifications for highway bridges. (1989). American Association of State Highway and Transportation Officials, Washington, D.C.
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Copyright © 1991 ASCE.
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Published online: Oct 1, 1991
Published in print: Oct 1991
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