Use of Adjacent Knot Data in Predicting Bending Strength of Dimension Lumber by X-Ray
Keywords:Knot depth ratio, X-ray, KDRA, knot cluster, knot spacing, bending strength, strength prediction, adjacent knot, lumber, grading
AbstractIn a previous study, the knot depth ratio (KDR) evaluation method was proposed to quantify the area of knots in a cross-section. That study reported that bending strength can be predicted by KDR analysis. However, the KDR model did not take into consideration the additional strength reduction caused by adjacent knots. It was found that the prediction of lumber strength was improved when adjacent knots were taken into consideration. Analysis using the KDRA (KDR adding knots) model revealed that the optimum cross-sectional interval, an input variable, is directly affected by knot size parallel to lumber length (KSPLL). KSPLL depends on the sawing method and log characteristics, and for species containing large knots, the cross-sectional interval is likely to be extremely wide. This can cause several adjacent small knots to be excluded from the analysis, requiring modification of the KDRA model algorithm. This modification resulted in improvement in the precision of the strength prediction, although the input variable of the cross-sectional interval was not used. The R2 values obtained using this method were 0.60 and 0.56 for Japanese larch and red pine, respectively.
Fain AK (2003) Fundamentals of digital image processing. Prentice Hall.nJohansson CJ, Brundin J, Gruber R (1992) Stress grading of Swedish and German timber. A comparison of machine stress grading and three visual grading systems. Swedish National Testing and Research Institute. SP Report 1998:38.nKSA (2002) Softwood structural lumber, Korean Standard Association, KS F 2162.nOh JK, Kim KM, Lee JJ (2008) Development of knot quantification method to predict strength using X-ray scanner. J Korean Wood Sci Technol 36(5):33-41.nOh JK, Shim K, Kim KM, Lee JJ (2009) Quantification of knots in dimension lumber using a single X-ray radiation. J Wood Sci 55(4):264-272.nRiberholt H, Madsen PH (1979) Strength of timber structures, measured variation of the cross sectional strength of structural lumber. Report R 114, Struct Research Lab, Technical University of Denmark.nSchajer GS (2001) Lumber strength grading using X-ray scanning. Forest Prod J 51(1):43-50.nSchniewind AP, Lyon DE (1971) Tensile strength of redwood dimension lumber. II. Prediction of strength values. Forest Prod J 21(8):45-55.nWWPA (2005) Western lumber grading rules. Western Wood Products Association, 05:14.3-148.n
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