Investigation of the Procedure for Estimating Concomitance of Lumber Strength Properties


  • David W. Green
  • James W. Evans
  • Richard A. Johnson


Correlation coefficient, concomitance, bending strength, tensile strength, computer simulation


An analytical method that utilizes information generated through proofloading to estimate the correlation between lumber strength properties is reviewed. A computer simulation was conducted to determine the effects of sample size and proofload level and also the degree of true correlation between lumber properties on the estimates of the correlation coefficient. Results indicate that reasonable estimates of the correlation coefficient can be obtained using sample sizes of 100 or more with a minimum proofload that would be expected to break 40% (proofload level = 0.40) of the specimens tested. Additional studies are suggested, however, before the technique is used.


Adby, R. R., and M. A. H. Dempster. 1974. Introduction to optimization methods. Halsted Press, New York, NY.nGalligan, W. L., R. A. Johnson, and J. R. Taylor. 1979. Examination of the concomitant properties of lumber. Proceedings of the Conference on Performance of the Metal Plate Wood Truss. Proceedings P-79-28, Forest Prod. Res. Soc., Madison, WI.nIMSL. 1979. IMSL Library, Reference Manual. Houston, TX.nJohnson, R. A., and W. L. Galligan. 1983. Estimating the concomitance of lumber strength properties. 15(3):235-244.nNewlin, J. A., and G. W. Trayer. 1956. Stresses in wood members subjected to combined column and beam action. USDA For. Serv. Rep. 1311. Forest Prod. Lab., Madison, WI.nNorris, C. B. 1962. Strength of orthotropic materials subjected to combined stresses. USDA For. Serv. Rep. 1816. Forest Prod. Lab., Madison, WI.nSenft, J. F., and S. K. Suddarth. 1970. Strength of structural lumber under combined bending and tension loading. For. Prod. J.20(7):17-21.nSuddarth, S. K., F. Woeste, and W. L. Galligan. 1978. Probabilistic engineering applied to wood members in bending tension. USDA For. Serv. Res. Pap. FPL 302. Forest Prod. Lab., Madison, WI.nTichy, R. 1981. Stochastic concepts in the design of wood structures: The concomitant problem. Ph.D. thesis, Washington State University, Pullman, WA.nZahn, J. 1982. Strength of lumber under combined bending and compression. USDA For. Serv. Res. Pap. 391. Forest Prod. Lab., Madison, WI.n






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