Nondestructive Evaluation of Modulus of Elasticity of Southern Pine LVL: Effect of Veneer Grade and Relative Humidity
Keywords:
Laminated veneer lumber (LVL), Nondestructive testing (NDT), stress-wave propagation, transverse vibration, veneer grade, relative humidity, southern pineAbstract
Nondestructive testing (NDT) methods, stress-wave propagation, and transverse vibration were used to evaluate the modulus of elasticity (MOE) of laminated veneer lumber (LVL). Five types of LVL, fabricated with southern pine veneers of B. C, and D grades and liquid phenolic formaldehyde adhesive, were tested flatwise at environmental conditions of 65% and 95% relative humidity (RH) and 75°F (23.9°) to examine the influence of veneer grade and RH on some nondestructive mechanical properties of LVL. All LVLs, 1.5 in. (3.81 cm) thick X 3.5 in. (8.89 cm) high X 96 in. (243.84 cm) long, consisted of 13 plies of southern pine veneer, and their structural designs were: (I) all B grade veneers, (II) 2 plies of B grade veneer on both faces and all C grade veneers in the core plies, (III) 2 plies of B grade veneer on both faces and all D grade veneer in the core plies, (IV) all C grade veneers, and (V) all D grade veneers. Results indicated that MOE of LVL predicted by NDT was influenced by the veneer grade, and specimens fabricated with better grade veneers showed a higher value of MOE. A significant decrease in the MOE determined by both NDT methods was found when RH increased from 65% to 95% at 23.9° (75°F). The MOE measured by the stress-wave method was found to be more sensitive to the RH change than that determined by the transverse-vibration method. A lognormal distribution accurately described the distributions of MOEs determined by both nondestructive methods at both RH levels. As expected, a significant increase in moisture content (MC) in the LVL resulted from increasing RH levels. However, changes in densities of the tested materials due to the RH changes were found to be smaller. Results also indicated that regardless of the RH level. MOE determined from the stress-wave test was consistently higher than that obtained from the transverse-vibration test. For comparison. the results of tests on southern pine No. 1 and No. 2 grade lumber, commonly used in light-frame construction, are also presented. Analysis of the correlation between the static bending and NDT MOEs was made and results suggested that edgewise static bending MOE of LVL can be predicted with reasonable accuracy by the stress-wave testing. Good correlations were not observed between the edgewise static bending MOE and the nondestructive MOE evaluated by flatwise transverse vibration. However, excellent correlations between static bending and both NDT MOEs were observed in southern pine dimension lumber. Correlations between the MOEs evaluated by both nondestructive methods were found to be fair for LVL specimens.References
American Plywood Association (APA). 1983. U.S. Product Standard PS-1-83: For construction and industrial plywood with typical APA treatments. Tacoma, WA. Pp. 8-11.nAmerican Society For Testing and Materials (ASTM). 1994. Standard methods of static tests of timbers in standard sizes. D-198-84. American Book of ASTM Standards, Sect. 4, Vol. 04.10. Philadelphia, PA.nBell. E. R., E. C. Peck, and N. T. Kruiger. 1954. Modulus of elasticity of wood determined by dynamic methods. Rep. 1977. USDA Forest Service. Forest Products Laboratory, Madison, WI.nBiblis, E. J., and J. B. Mercado. 1991. Flexural and shear properties of southern yellow pine laminated veneer lumber. Pages 3, 413-8.420, Vol 3 in Proc. 1991 International Timber Engineering Conf. TRADA, London, UK.nBohlen, J. C. 1974. Tensile strength of Douglas-fir laminated-veneer lumber. Forest Prod. J. 24(1): 16-23.nBohlen, J. C. 1975. Shear strength of Douglas-fir laminated-veneer lumber. Forest Prod. J. 25(2): 16-23.nEchols, R. M., and R. A. Currier. 1973. Comparative properties of Douglas-fir boards made from parallellaminated veneers vs. solid wood. Forest Prod. J. 23(2): 45-47.nFpl-press-lam Research Team. 1972. Feasibility of producing a high-yield laminated structural product. Res. Pap. FPL 175. USDA Forest Service. Forest Products Laboratory, Madison. WI.nFpl-press-lam Research Team. 1977. Progress in technical development of laminated veneer structural products. Res. Pap FPL 279. USDA Forest Service. Forest Products Laboratory. Madison, WI.nFridley, K. J., R. C. Tang, and L. A.Soltis. 1992. Hygrothermal effects on mechanical properties of lumber. J. Struct. Eng. Structural Div. ASCE 118(2):567-581.nGallgan, W. L., and R. W. Courteau. 1965. Measurement of elasticity of lumber with longitudinal stress waves and the piezo-electric effect of wood. Pages 223-244 in Proc. 2nd. Nondestructive Testing of Wood Symp., April 1965, Washington State Univ., Pullman, WA.nGallgan, W. L., D. V. Snodgrass, and G. W. Crow. 1977. Machine stress rating: Practical concerns for lumber producers. Gen. Tech. Rep. FPL-GTR-7 USDA Forest Service, Forest Products Laboratory, Madison, WI.nGerhards, C. C. 1982. Effect of knots on stress waves in lumber. Res. Pap. FPL-RP-384. USDA Forest Service, Forest Products Laboratory, Madison, WI.nGreen, D. W., and K. A. McDonald. 1993a. Investigation of the mechanical properties of red oak 2 by 4's. Wood Fiber Sci. 25(1):35-45.nGreen, D. W., and K. A. McDonald. 1993b. Mechanical properties of red maple structural lumber. Wood Fiber Sci. 25(4): 365-374.nHoyle, R. J. 1964. Research results on machine stress rated southern pine lumber. Potlatch Forests, Inc., Lewiston. ID.nHoyle, R. J. 1968. Background to machine stress rating. Forest Prod. J. 18(4):87-97.nJung, J. 1979. Stress-wave grading techniques on veneer sheets. Gen. Tech. Rep. FPL-27. USDA Forest Service, Forest Products Laboratory. Madison. WI.nJung, J. 1982. Properties of parallel-laminated veneer from stress-wave tested veneers. Forest Prod. J. 32(7): 30-35.nKoch, P. 1973. Structural lumber laminated from 1/4-inch rotary-peeled southern pine veneer. Forest Prod. J. 23(7): 17-25.nKoch, P., and G. E. Woodson. 1968. Laminating butt-jointed, log-run southern pine veneers into long beams of uniform high strength. Forest Prod. J. 18(10):45-51.nKretschmann, D. E., R. C, Moody, R. F., Pellerin, B, A. Bendtsen, J. M. Cahill., R. H. McAlister, and D. W. Sharp. 1993. Res. Pap. FPL-RP-521. Effect of various propertions of juvenile wood on laminated veneer lumber. USDA Forest Service. Forest Products Laboratory, Madison, WI.nKunesh. R. H. 1978. MICRO = LAM: Structural laminated veneer lumber. Forest Prod. J. 28(7):41-44.nMcAlister. R. H. 1976. Modulus of elasticity distribution of loblolly pine veneer as related to location within the stem and specific gravity. Forest Prod. J. 26(1):37-40.nMoody, R. C., and C. C. Peters. 1972. Strength properties of rotary knife-cut laminated southern pine. Res. Pap. FPL 178. USDA Forest Service, Forest Products Laboratory, Madison. WI.nNational Institute of Standards and Technology (Nist). 1995. Voluntary Product Standard PSI-95. Construction and Industrial Plywood (with typical APA trademarks) 41 pp.nNelson, S. A. 1972. Structural application of MICRO=LAM lumber. Civ. Eng. 42(7):57.nO'halloran, M. R. 1969. Nondestructive parameters for lodgepole pine dimension lumber. M.S. thesis, Colorado State Univ., Fort Collins. CO.nPellerin, R. F. 1963. Correlation of strength properties of 1-inch lumber. Washington State Univ. Div. of Industrial Research. Potlatch Forests, Lewiston, ID.nPellerin, R. F. 1965. A vibrational approach to nondestructive testing of structural lumber. Forest Prod J. 15(3):93-101.nPellerin, R. F., and W. L. Galligan. 1973. Nondestructive method of grading wood materials. Canadian Patent 918286.nPorter, A. W., D. J. Kusec, and S. L. Olson. 1972. Digital computer for determining modulus of elasticity of structural lumber. WFPL INf. Rep. VP-X-99. Dept. of the Environment, Canadian Forest Service, Vancouver, BC.nRfad, B. E., and G. D. Dean. 1978. The determination of dynamic properties of polymers and composites. John Wiley & Sons., New York. NY. 207 pp.nRoss, R. J., and R. F. Pellerin. 1991. Stress wave evaluation of green material. Preliminary results using dimension lumber. Forest Prod. J. 41(6):57-59.nRoss, R. J., and R. F. Pellerin. 1994. Nondestructive testing for assessing wood members in structures. A Review. Gen. Tech. Rep FPL-GTR-70. USDA Forest Service, Forest Products Laboratory, Madison. WI.nRoss, R. J., R. F. Pellerin, and M. Sato. 1993. Nondestructive evaluation of timber in the United States. Pages 1229-1235 in Nagataki, Nireki, and Tomosawa, eds. Proc. 6th Intl. Conf. of Durability of Building Materials and Components.nSharp, D. J. 1985. Nondestructive testing techniques for manufacturing I.VI. and predicting performance Pages 99-108 in Proc. 5th Nondestructive Testing of Wood Symp. Sept. 9-11. Washington State University, Pullman. WA.nStump, J. P., L. A. Smith, and R. L. Gray. 1981. Laminated veneer lumber made from plantation-grown conifers. Forest Prod. J. 31(4):34-40.nTang, R. C., and N. N. Hsu. 1972. Dynamic Young's modulus of wood related to moisture content. Wood Science 5(1):7-14.nTang, R. C., J. H. Pu, and P. Schkoeder. 1995. Structural performance of LVL: Effect of veneer grade and relative humidity. Presented at 1995 IUFRO XX World Congress in Tampere, Finland, Aug. 6-12, 1995.nVining, S. 1991. An overview of engineered wood products. Pages 27-34 in F. T. Kurpiel and T. D. Faust, eds. Proc. Engineered Wood Products, Processing, and Design. Southeastern Sect, FPS.nVlosky, R. P., P. M. Smith, P. R. Blankenhorn, and M. P. Haas. 1994. Laminated veneer lumber; A United States market overview. Wood Fiber Sci. 26(4):456-466.nWang, Z. R. J. Ross, and J. F. Murphy. 1993. A comparison of several NDE techniques for determining the modulus of elasticity of lumber. World Forest Research 6(4):86-88 (in Chinese).n
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