Edinburgh Napier University

  Shear constant of timber glulam materials plays an important role in structural modelling, such as lateral torsional buckling of the glulam beam, floor vibration and stabilities of long span glulam girders. In normal design approach, a fraction of the modulus of elasticity (MOE) from the bending test is adopted. However, recent research (Zhang 2011; Khokhar 2010; Khokhar 2009) have indicated there is little evidence of the strong correlation between the Shear Constant and MOE. A torsional test method has also been proposed in which inclinometers are employed to measure the rotation of the specimens. Although, inclinometer is convenient on measuring the surface rotation, but the size of the sensor has also limited the measure only to the level of average rotation of the area covered by the sensor rather than the accurate rotation at a given location thus it is not possible to measure the shear strain distribution along the height of the cross-sections which is essential to understand the torsional behaviour of the glulam beams. The development of new techniques to measure the rotation for a smaller area is very important on determining the shear constant with torsion test method. In this paper, the photogrammetric technique has been developed for the torsion test method to evaluate the shear constant of glulam beams. The initial results show an improved accuracy and more detailed shear displacement has been captured.