| In this paper, visual grading according to North American lumber grading rules(NLGA),full size bending test according to British standard(BS/EN 408), Chinese standard(GB/T50329), American standard(ASTM D4761) and Intemational standard (ISO 13910) and fullsize tension test parallel to grain according to Newzealand standard(NZS 4063), Internationalstandard, American standard and British standard were conducted on Chinese Firplantation(Cunningharnia lanceolata) 2″×4″dimension lumber of Fujian Province, whichactually had a corss section of 45mm×90mm. The purpose of making such intensive andsystematic investigation on the influence of various test methods on the mechanical propertiesof Chinese Fir plantation dimension lumber is to supplement the 'GB/T 50329-2002 ChineseTimber Structure Standard Testing Procedure', to provide scientific evidence in impulsingtesting and evaluating system of mechanical properties of Chinese structural dimension lumber,to build up equivalence relationships between Chinese standard and those of other countries,to promote Chinese mechanical properties testing standard to keep pace with internationalrequirement as soon as possible. In addition, this study can help to broaden the approaches toutilize the Chiese Fir plantation as a kind of high-value added product, to change the passivesituation that dimension lumber used in China entirely relys on import, to push forward theforestry economy of our country healthily, stably and harmonically.The main results of this dissertation were as following:1. There was significant difference of visual grading results of main plantation in NorthAmerican and Fujian Chinese Fir plantation according to North-America lumber gradingrules. Various defects contributed differently to the degrading of dimension lumber. Themaximum-yield-rate sawing pattern was used, among the degrade of Chiese Fir plantationdimension lumber, approximately 32 percent was caused by knot, 17 percent was caused bywane.However, Among the degrade of main plantation dimension lumber in NorthAmerican, approximately 10 percent was caused by knot, 70 percent was caused bywane. Consequently, it was indicated that as far as Chiese Fir plantation dimension lumber wasconcerned, the grade yield depended on knot rather than wane to a large extent.2. Characteristic values of edgewise bending modulus of elasticity, flatwise bending modulus of elasticity, edgewise bending modulus of rupture and tension strength parallel tograin were obtained by non-parameter statistic method. After the Characteristic values weretransformed into allowable properties, the allowable edgewise bending modulus of elasticity ofall the grades was smaller than basic design value of the corresponding grade of WesternHemlock (Tsuga heterophylla) in NLGA. On the contrary, the allowable edgewise bendingmodulus of rupture and tension strength parallel to grain of all the grades were larger than basicdesign value of the corresponding grade of Western Hemlock.3. Analysis of variance showed that various test method had significant influence ontension strength parallel to grain (Pr＜0.0001). Duncan's multiple range test result showed thatmean tension strength parallel to grain obtained by ASTM was higher than NZS, BS higherthan NZS, ISO higher than NZS at significance level of 0.05. The influence of various testmethods on the edgewise bending modulus of elasticity and modulus of rupture was notsignificant in a statistical sense. Furthermore, the influence of various test methods on theflatwsie bending modulus of elasticity depended on visual grade as the followings:(1)For Select Structural (SS) grade, various test method had significant influence onflatwise bending modulus of elasticity (Pr=0.0291). Duncan's multiple range test result showedthat mean flatwise bending modulus of elasticity obtained by BS was higher than that obtainedby ISO at significance level of 0.05.(2)For No.1 grade, various test method had no significant influence on flatwise bendingmodulus of elasticity.(3)For No.2 grade, various test method had significant influence on flatwise bendingmodulus of elasticity (P_r=0.0388). Duncan's multiple range test result showed that mean flatwisebending modulus of elasticity obtained by ASTM was higher than that obtained by BS, ISOhigher than BS at significance level of 0.05.(4)For No.3 grade, various test method had significant influence on flatwise bendingmodulus of elasticity (P_r=0.0281). Duncan's multiple range test result showed that mean flatwisebending modulus of elasticity obtained by ASTM was higher than that obtained by BS, ASTMhigher than GB at significance level of 0.05.4. The equivalent relationships of bending properties obtained by BS, GB, ASTM and ISOin individual visual grade were gained on basis of 5 to 95 percentile properties average obtained by GB. At same time, the equivalent relationships of tension property parallel to grainobtained by NZS, ISO, ASTM and BS in individual visual grade were gained on basis of 5 to95 percentile properties average obtained by ISO.(1) All indexed to 5 to 95 percentile mechanical properties average obtained by GB, theratio of edgewise bending modulus of elasticity of SS, No.1, No.2 and No.3 grade obtained byBS was 1.02, 0.95, 0.97, 0.97 in sequence, the ratio of flatwise bending modulus of elasticityobtained by BS was 1.04, 0.98, 0.94, 1.01 in sequence, the ratio of edgewise bending modulusof rupture obtained by BS was 1.02, 0.92, 0.82, 1.18 in sequence. The ratio of edgewisebending modulus of elasticity of SS, No. 1, No.2 and No.3 grade obtained by ASTM was 0.99,1.08, 1.17, 1.14 in sequence, the ratio of flatwise bending modulus of elasticity obtained byASTM was 0.99, 1.08, 1.16, 1.20 in sequence, the ratio of edgewise bending modulus ofrupture obtained by ASTM was 1.00, 1.21, 1.20, 1.27 in sequence. The ratio of edgewisebending modulus of elasticity of SS, No.1, No.2 and No.3 grade obtained by ISO was 0.97,1.12, 1.12, 1.14 in sequence, the ratio of flatwise bending modulus of elasticity was 0.96, 1.11,1.06, 1.12 in sequence, the ratio of edgewise bending modulus of rupture was 0.98, 1.17, 1.11,1.23 in sequence.(2)All indexed to 5 to 95 percentile mechanical properties average obtained by ISO, theratio of tension strength parallel to grain of SS, No.1, No.2 and No.3 grade obtained by NZSwas 0.82, 0.96, 0.85, 0.92 in sequence. The ratio of tension strength parallel to grain of SS, No. 1,No.2 and No.3 grade obtained by ASTM standardwas 0.98, 1.07, 0.88, 0.87 in sequence. Theratio of tension strength parallel to grain of SS, No.1, No.2 and No.3 grade obtained by BSstandard was 0.98, 1.03, 1.02, 0.96 in sequence.5. Regression analysis results showed that the relationships between tension strengthparallel to grain (UTS) and bending modulus of rupture (MOR) of Chiese Fir plantationdimension lumber on various levels from 5 percentile to 95 percentile were expressed asUTS=a×MOR~b with coefficient of determination (R~2) ranging from 0.8325 to 0.9717.
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