1993 Volume 42 Issue 473 Pages 121-125
This paper deals with the validity of the resonance frequency of longitudinal vibration as a parameter for prediction of the Young's modulus of structural timbers and the relationships among quality parameters such as density, Young's modulus and specific Young's modulus. Seven hundred and seventy-nine pieces of 2″ by 4″ dimension lumber, eighty pieces of sugi post and forty pieces of hinoki post for the traditional Japanese wood construction were tested. Ten sugi logs and nine hinoki logs were also examined. The resonance frequency by tapping the cross section of the specimens was determined by using a Fast Fourier Transformation spectrum analyzer.
The specific Young's modulus, E/ρ (E: Young's modulus, ρ: density) was independent of the density of specimens. However, it was recognized that the specific Young's modulus was high correlation with Young's modulus of structural timbers. These facts were ascertained not only in the dimension lumber at dry condition but also in the sawn square timbers at green condition. The linear regression analysis proved the validity of the resonance frequency of longitudinal vibration as a parameter for prediction of the Young's modulus of structural timbers. This result enables the simple mechanical grading of structural timbers based on the Young's modulus measurement, which does not require mass measurement of heavy timbers such as large beams and logs.
