Load‐Duration Effects in Structural Lumber: Strain Energy Approach
Publication: Journal of Structural Engineering
Volume 118, Issue 9
Abstract
A critical strain‐energy‐density failure criterion is introduced to describe the load‐duration (creep‐rupture) behavior of structural lumber. From extensive ramp, constant, and step‐constant load tests in various constant and cyclic environments, a critical strain‐energy density is identified, which forecasts impending failure. Impending failure is defined as the initiation of member failure, excluding partial failures that do not influence subsequent member behavior. Most previous load‐duration research defined failure as the complete collapse of a test member and modeled the response using cumulative damage theory. Select structural and no. 2 grade Douglas‐fir nominal 2 in. by 4 in. lumber are used here. The critical strain‐energy density is found to be invariant with respect to load history, load level, grade, and hygrothermal condition. A model is developed and used to predict the observed load‐duration behavior of the Douglas‐fir lumber sample. A comparison between the damage accumulation approach to modeling load‐duration effects and the developed strain energy approach is also presented.
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References
1.
Barrett, J. D., and Foschi, R. O. (1978). “Duration of load and probability of failure in wood. Part I: Modelling creep rupture.” Canadian J. of Civ. Engrg., 5(4), 505–514.
2.
Christensen, R. M. (1982). Theory of viscoelasticity: An introduction. 2nd Ed., Academic Press, New York, N.Y.
3.
Ethington, R. L. (1970). “Some stress‐grading criteria and methods of grade selection for dimension lumber.” Res. Paper FPL 148, U.S.D.A., Forest Serv., Forest Products Lab., Madison, Wis.
4.
Foschi, R. O., and Barrett, J. D. (1982). “Load‐duration effects in western hemlock lumber.” J. Struct. Div., ASCE, 108(7), 1494–1510.
5.
Foschi, R. O., Folz, B. R., and Yao, F. Z. (1989). “Reliability‐based design of wood structures.” Struct. Res. Series, Rep. No. 34, Dept. of Civ. Engrg., Univ. of British Columbia, Vancouver, Canada.
6.
Foschi, R. O., and Yao, Z. C. (1986). “Another look at three duration of load models.” Proc., XVII IUFRO Congress, Paper No. 19‐9‐1, Int. Union of Forestry Res. Organizations.
7.
Fridley, K. J., Tang, R. C., and Soltis, L. A. (1989). “Thermal effects on load‐duration behavior of lumber. Part I. Effect of constant temperature.” Wood and Fiber Sci., 21(4), 420–431.
8.
Fridley, K. J., Tang, R. C., and Soltis, L. A. (1990). “Thermal effects on load‐duration behavior of lumber. Part II. Effect of cyclic temperature.” Wood and Fiber Sci., 22(2), 204–216.
9.
Fridley, K. J., Tang, R. C., and Soltis, L. A. (1991). “Moisture effects on load‐duration behavior of lumber. Part I. Effect of constant relative humidity.” Wood and Fiber Sci., 23(1), 114–127.
10.
Fridley, K. J., Tang, R. C., and Soltis, L. A. (1992a). “Hygrothermal effects on the mechanical properties of lumber.” J. Struct. Engrg., ASCE, 118(2), 567–581.
11.
Fridley, K. J., Tang, R. C., and Soltis, L. A. (1992b). “Moisture effects on load‐duration behavior of lumber. Part II. Effect of cyclic relative humidity.” Wood and Fib. Sci., 24(1), 89–98.
12.
Fridley, K. J., Tang, R. C., and Soltis, L. A. (1992c). “Creep behavior model for structural lumber.” J. Struct. Engrg., ASCE, 118(8), 2261–2277.
13.
Fridley, K. J., Tang, R. C., Soltis, L. A., and Yoo, C. H. (1992d). “Hygrothermal effects on the load‐duration behavior of lumber.” J. Struct. Engrg., ASCE, 118(4), 1023–1038.
14.
Gerhards, C. C. (1979). “Time‐related effects on wood strength: A linear‐cumulative damage theory.” Wood Sci., 11(3), 139–144.
15.
Gerhards, C. C. (1988). “Effect of grade on load‐duration of Douglas‐fir in bending.” Wood and Fib. Sci., 20(1), 146–161.
16.
Gerhards, C. C., and Link, C. L. (1987). “A cumulative damage model to predict load duration characteristics of lumber.” Wood and Fib. Sci., 19(2), 147–164.
17.
National design specifications for wood construction. (1986). National Forest Products Association, Washington, D.C.
18.
Wood, L. W. (1951). “Relation of strength of wood to duration of load.” Rep. No. 1916, U.S.D.A., Forest Service, Forest Products Lab., Madison, Wis.
Information & Authors
Information
Published In
Journal of Structural Engineering
Volume 118 • Issue 9 • September 1992
Pages: 2351 - 2369
Copyright
Copyright © 1992 ASCE.
History
Published online: Sep 1, 1992
Published in print: Sep 1992
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