Determining Modulus of Elasticity of Structural Lumber with Vibration Methods

In order to study fundamental methods for determining modulus of elasticity (MOE) of structural lumber with vibration methods, the theoretical basis of the measurement is introduced and a hanging style testing system, which consists of an impulse hammer, accelerometer, computer, etc., is built up. It is found that transverse vibration method can determine resonant frequencies of structural lumber specimens effectively. On the specimen, the distance between impact point and detection point should be as far as possible, i.e. the two points should be situated near the two ends of the specimen. The test results are not influenced by using different supports-springs or soft strings. Compared with modulus of elasticity values derived by traditional bending methods, the modulus of elasticity obtained by the transverse vibration method are larger. Also, the both have a very good correlation. Therefore, the vibration testing method can be used to determine lumber MOE. Finally, in order for research results to be truly applied to practices, a portable lumber MOE testing equipment based on simply supported beam vibration was developed. This equipment is suitable for determining dynamic MOE and, consequently, for stress grading structural lumber.