Edinburgh Napier University

  This paper presents the work that was undertaken to use torsion tests to evaluate the shear modulus of wood joists. The relationship of the shear modulus with modulus of elasticity, obtained from bending tests, was examined. Testing standard EN408 have recommended torsion test to determine the shear modulus of structural-size timber. However, shear modulus values in EN338 are determined from modulus of elasticity using the modulus of elasticity to shear modulus ratio of 16 to 1(16:1). This work has found no evidence of correlation between these two mechanical properties. It was found that modulus of elasticity to shear modulus ratio depends on wood species and the strength grade of timber. A substantial variation in shear modulus (10 to 30%) was noticed along the length of test joists. However, in this study, it was seen that the variation was not influenced by knot or other wood defects.