The dimension lumber （45mm×90mm×3700mm） of plantation Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） was graded to four different classes as SS, No. 1, No.2 and No.3, according to national lumber ...The dimension lumber （45mm×90mm×3700mm） of plantation Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） was graded to four different classes as SS, No. 1, No.2 and No.3, according to national lumber grades authority （NLGA） for structure light framing and structure joists and planks. The properties of apparent density was determined at 15% moisture content, bending strength and stiffness were tested according to American Society for Testing and Materials （ASTM） D198-99, and dynamic modulus of elasticity （Eusw） was measured by ultrasonic technique, for predicting the flexural properties of different grade lumbers. The results showed that Eosw was larger than the static MOE. The relationship between Eusw and static MOE was significant at 0.01 level, and the determination coefficients （R2） of the four grade lumbers followed the sequence as R^2No.2 （0.616）〉 R^2ss （0.567）〉 R^2No1 （0.366）〉 R^2No.3 （0.137）. The R^2 of Fusw and MOR were lower than that of the Etru and MOR for each grade. The Eusw of all the grade lumbers, except No.3-grade, had significant correlation with the static MOE and MOR, thus the bending strengthof those grade lumbers can be estimated by the E The Etru valuesof four grade lumbers followed a sequence as No.2-grade （10.701 GPa） 〉 SS-grade （10.359 GPa） 〉 No.l-grade （9.840 GPa） 〉 No.3-grade （9.554 GPa）. For the same grade dimension lumber, its Eusw value was larger than static MOE. Mean values of MOR for four grade lumbers follow a sequence as No.2-grade （48.67 MPa） 〉 SS-grade （48.16 MPa） 〉 No.3-grade （46.55 MPa） 〉 No. 1-grade （43.39MPa）.展开更多
We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and ...We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and side nail- holding power of the wood specimens both declined, but the differences between salinity treatments were not sig- nificant. However, compared to the surface and side nail- holding power, the power on the edge was generally less and the difference was not obvious in different salt con- centrations. In the same salt concentration, with the extension of the processing cycle, the performance of holding power of nails showed a downward trend, expect the temporary rise in the middle.展开更多
基金Standard system on forestry engineering of Ministry ofScience and Technology ( 2004DEA70900-1).
文摘The dimension lumber （45mm×90mm×3700mm） of plantation Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） was graded to four different classes as SS, No. 1, No.2 and No.3, according to national lumber grades authority （NLGA） for structure light framing and structure joists and planks. The properties of apparent density was determined at 15% moisture content, bending strength and stiffness were tested according to American Society for Testing and Materials （ASTM） D198-99, and dynamic modulus of elasticity （Eusw） was measured by ultrasonic technique, for predicting the flexural properties of different grade lumbers. The results showed that Eosw was larger than the static MOE. The relationship between Eusw and static MOE was significant at 0.01 level, and the determination coefficients （R2） of the four grade lumbers followed the sequence as R^2No.2 （0.616）〉 R^2ss （0.567）〉 R^2No1 （0.366）〉 R^2No.3 （0.137）. The R^2 of Fusw and MOR were lower than that of the Etru and MOR for each grade. The Eusw of all the grade lumbers, except No.3-grade, had significant correlation with the static MOE and MOR, thus the bending strengthof those grade lumbers can be estimated by the E The Etru valuesof four grade lumbers followed a sequence as No.2-grade （10.701 GPa） 〉 SS-grade （10.359 GPa） 〉 No.l-grade （9.840 GPa） 〉 No.3-grade （9.554 GPa）. For the same grade dimension lumber, its Eusw value was larger than static MOE. Mean values of MOR for four grade lumbers follow a sequence as No.2-grade （48.67 MPa） 〉 SS-grade （48.16 MPa） 〉 No.3-grade （46.55 MPa） 〉 No. 1-grade （43.39MPa）.
基金financially supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)Jiangsu Overseas Research&Training Program for University Prominent Young&Middle-aged Teachers and Presidents
文摘We studied the effect of salinity on nail-hold- ing power in wood construction. In saline solution, the holding power of nails was less than in purified water. With the increase of salt concentration, the surface and side nail- holding power of the wood specimens both declined, but the differences between salinity treatments were not sig- nificant. However, compared to the surface and side nail- holding power, the power on the edge was generally less and the difference was not obvious in different salt con- centrations. In the same salt concentration, with the extension of the processing cycle, the performance of holding power of nails showed a downward trend, expect the temporary rise in the middle.
