Creep and Creep-Recovery Models for Wood Under High Stress Levels


  • Zhiyong Cai
  • Kenneth J. Fridley
  • Michael O. Hunt
  • David V. Rosowsky


Creep, recovery, duration-of-load, model, clear specimen, high stress level, southern pine


Forty small clear southern pine specimens were loaded under third-point bending to examine creep and creep-recovery behavior for wood under high stress levels. Stress levels of between 69% and 91% of the predicted static strength were applied for 23 h with 1 h allowed for recovery, and the resulting deflection vs. time behavior was studied. The experimental creep and creep-recovery behavior was modeled using modified power law functions. The results indicate that these functions provide the best fit to both primary and secondary experimental data. The empirical models can be used to simulate the viscoelastic behavior of wood under high stress levels. The simulation will provide a useful tool in future studies to examine duration-of-load (DOL) effect, which is one of the more important factors in wood structural design.


Belsley, D. A., E. Kuh, and R. E. Welsch. 1980. Regression diagnostics: Identifying influential data and sources of collinearity. John Wiley & Sons, Inc., New York, NY. Chapter 3.nBodig, J., and B. A. Jayne. 1982. Mechanics of wood and wood composites. Van Nostrand Reinhold Co., New York, NY, Chapter 5.nCai, Z. 1997. Experimental investigation of damage accumulation in wood. A thesis submitted to the faculty of Purdue University, West Lafayette, IN. Chapter 7.nCai, Z., G. P. McCabe, M. O. Hunt, K. J. Fridley, D. V. Rosowsky, and J. P. Bradtmueller. 1998. Predicting strength of matched sets of test specimens. Wood Fiber Sci. 30(4):396-404.nFridley, K. J., R. C. Tang, and L. A. Soltis. 1992. Creep behavior model for structural lumber. ASCE J. Struct. Eng. 118(8):2261-2277.nGerhards, C. C. 1985. Time-dependent bending deflections of Douglas-fir 2 by 4s. Forest Prod. J. 35(4):18-26.nGerhards, C. C. 1991. Bending creep and load duration of Douglas-fir 2 by 4s under constant load. Wood Fiber Sci. 23(3):384-409.nGittus, J. H. 1975. Creep, viscoelasticity, and creep fracture in solids. John Wiley and Sons, Inc., New York, NY. Chapter 7.nPentoney, R. E. 1962. Time-dependent mechanical properties of wood. In Proc. The Mechanical Behavior of Wood. August 27-Sept. 1, 1962, University of California, Berkeley, CA.nSchniewind, A. P., and J. D. Barrett. 1972. Wood as a linear orthotropic viscoelastic material. Wood Sci. Technol. 6:43-57.nSenft, J. F., and S. K. Suddarth. 1971. An analysis of creep-inducing stress in sitka spruce. Wood Fiber 2(4): 321-327.nSoltis, L. A., W. Nelson, and J. L. Hillis. 1989. Creep of structural lumber. In Proc. 3d Joint ASCE/ASME Mechanics Conference, 1989 July 9-12, San Diego, CA.nSuchsland, O., and G. E. Woodson. 1990. Fiberboard Manufacturing Practices in the United States. Forest Prod. Res. Soc., Madison, WI.n






Research Contributions