Effect of Moisture Content on Dowel-Bearing Strength
Keywords:Wood, moisture content, dowel-bearing strength, embedment strength, compression stress, mechanical fasteners
AbstractDowel bearing strength (embedment strength) is a critical component of wood connection design. Previous tests have concentrated on defining the relationship between dowel-bearing strength, specific gravity, and fastener characteristics such as diameter. However, because adoption of yield theory indefining connection strength is relatively new in the United States, few studies have been conducted that completely define the factors influencing dowel-bearing strength. One such factor is moisture content. In this study, the dowel-bearing strength of two groups of specimens was determined. One group was made up of approximately 200 clear Southern Pine pieces distributed evenly among five different moisture content environments (4%, 6%, 12%, 19%, and green) and loaded with 12.7-mm- (0.5-in.-) diameter bolts. The second group included Southern Pine, Douglas Fir-Larch, and Spruce-Pine-Fir specimens in two moisture content environments (6% and 20+%) that were loaded with 3.33-mm (0.131-in.) (8d) smooth shank nails. An empirical linear relationship was developed between dowel-bearing strength and moisture content using the first group of specimens, which compared favorably with results from the second group. These results show that the dowel-bearing strength-moisture content relationship was not dependent on species or fastener type, and therefore, those parameters were not included in the model. Auxiliary tests verified previous research that has shown that dowel-bearing strength (parallel-to-grain) is positively correlated with ultimate parallel-to-grain compression strength.
American Forest and Paper Association (AF&PA). 1991. Commentary on the national design specification for wood construction. American Forest and Paper Association, Washington, DC.nAmerican Forest and Paper Association (AF&PA). 1997. National design specification for wood construction. American Forest and Paper Association, Washington, DC.nAmerican Society of Civil Engineers (ASCE). 1996. Load and resistance factored design for engineered wood construction. American Society of Civil Engineers, Washington, DC.nAmerican Society for Testing and Materials (ASTM). 1998a. Establishing allowable properties for visuallygraded dimension lumber from in-grade tests of full-size specimens. ASTM D1990-97. American Society for Testing and Materials, West Conshohocken, PA.nAmerican Society for Testing and Materials (ASTM). 1998b. Standard test methods for specific gravity of wood and wood-base materials. ASTM D2395-93. American Society for Testing and Materials, West Conshohocken, PA.nAmerican Society for Testing and Materials (ASTM). 1998c. Standard test method for evaluating dowel bearing strength of wood and wood-base products. ASTM D5764-95. American Society for Testing and Materials, West Conshohocken, PA.nAune, P., and M. Patton-Mallory. 1986. Lateral load-bearing capacity of nailed joints based on the yield theory—Experimental verification. FLP-RP-470. USDA Forest Service, Forest Products Laboratory, Madison, WI.nCockrell, R. A. 1933. A study of the screw holding properties of wood. Technical Publication No. 44. Bulletin of the New York State College of Forestry, Syracuse, NY. 27 pp.nEhlbeck, J. 1979. Nailed joints in wood structures. Bulletin No. 166. Virginia Polytechnic Institute and State University, Blacksburg, VA. 143 pp.nFahlbusch, H. 1949. A contribution to the problem of the bearing strength of bolts in wood under static loads. Report No. 49-09, Institute for Mechanical Construction and Carpentry, Braunschweig, Germany (translated from German; Translation No. 218 from Research Information Service, New York; translated for USDA Forest Serv. Forest Prod. Lab., Madison, WI, in May, 1955).nForest Products Laboratory. 1999. The wood handbook: Wood as an engineering material. Gen. Tech. Rep. FPL-GTR-113. USDA Forest Serv. Forest Prod. Lab., Madison, WI.nGreen, D. W., and J. W. Evans. 1989. Moisture content and the mechanical properties of dimensioned lumber. Pages 44-55 in In-grade testing of structural lumber, Proc. 47363. Forest Products Research Society, Madison, WI.nGreen, D. W., and D. E. Kretschmann. 1994. Moisture content and the properties of clear Southern Pine. Research Paper FPL-RP-531. USDA Forest Serv. Forest Prod. Lab., Madison, WI. 28 pp.nJohansen, K. W. 1949. Theory of timber connections. International Association for Bridge and Structural Engineering.9:249-262.nKoponen, S. 1991. Embedding characteristics of wood in the grain direction. Report 25, Helsinki University of Technology, Laboratory of Structural Engineering and Building Physics. Espoo, Finland. 21 pp. + appendices.nKuipers, J., and P. Vermeyden. 1965. The ratio between strength and allowable loads on timber joints. In Proc. International Symposium on Joints in Timber Structures, London, UK.nLarsen, H. J., and E. Sorensen. 1973. Joints with conical steel pins. Pages 661-671 in Proc. IUFRO-5 Meeting. Vol. 2. 22 Sept.-12 Oct. 1973, Republic of South Africa.nMcLain, T. E. 1992. Strength of lag screw connections. ASCE J. Struct. Eng.118(10):2855-2871.nMcLain, T. E. 1997. Design axial withdrawal strength from wood: I. Wood screws and lag screws. Forest Prod. J.47(5):77-84.nMcLain, T. E., and S. Thangjitham. 1983. Bolted wood-joint yield model. ASCE J. Struct. Eng.109(8):1820-1835.nSmith, I., L. R. J. Whale, C. Anderson, B. O. Hilson, and P. D. Rodd. 1988. Design properties of laterally loaded nailed or bolted wood joints. Can. J. Civ. Eng.15:633-643.nSoltis, L. A., and T. L. Wilkinson. 1987. Bolted connection design. Gen. Tech. Rep. FPL-GTR-54. USDA Forest Serv., Forest Prod. Lab., Madison, WI.nSoltis, L. A., F. K. Hubbard, and T. L. Wilkinson. 1986. Bearing strength of bolted timber joints. ASCE J. Struct. Eng.112(9):2141-2154.nSuddarth, S. K. 1990. Test performance of 11/2-inch bolts in glulam—row effect and effect of subsequent drying. Wood Design Focus1(1).nTrayer, G. W. 1932. The bearing strength of wood under bolts. Technical Bulletin No. 332. USDA Forest Serv. Forest Prod. Lab., Madison, WI. 40 pp.nU.S. Department of Agriculture (USDA). 1935. The wood handbook. U.S. Department of Agriculture, Washington, DC.nWeisberg, S. 1985. Applied linear regression, 2nd Ed. John Wiley & Sons. Canada.nWilkinson, T. L. 1971. Bearing strength of wood under embedment loading of fasteners. Res. Pap. FPL-RP-163. USDA Forest Serv., Forest Prod. Lab., Madison, WI. 12 pp.nWilkinson, T. L. 1991. Dowel bearing strength. Res. Pap. FPL-RP-505. USDA Forest Serv., Forest Prod. Lab., Madison, WI. 9 pp.nWilkinson, T. L. 1993. Bolted connection design values based on European yield model. ASCE J. Struct. Eng.119(7):2169-2186.nWilson, T. R. C. 1932. Strength-moisture relations for wood. Tech. Bull. 282. U.S. Department of Agriculture, Washington, DC.nWinistorfer, S. G. 1994. Validation of the European yield model for nailed connections. in Proc. Structures Congress '94. Atlanta, GA. April 24-28 1994. American Society of Civil Engineers, New York, NY.n
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