Timber is one of the few truly renewable building materials, and thanks partly to the rise in off-site prefabrication its use is becoming ever more common.  Wood is a very complex anisotropic natural composite and, despite the long history of timber construction, the factors that govern its mechanical properties are still not well understood.

At Edinburgh Napier University, researchers at the Centre for Timber Engineering are using a 1kNm Tinius Olsen torsion tester to examine the shear strength and stiffness of Sitka spruce- the UK’s main commercial species.  The results show that, surprisingly, there is no correlation between shear stiffness and bending stiffness and that the weakest part of the timber is not always the part with least knots.  Inclinometers are used to measure twist over different sections of the specimens, which are up to 3.6 m long and can twist more than 90 degrees before breaking. 

More information and papers on Timber testing are available in the Resouce area of this site - you will need to log-in to view these papers.