End effect on determining shear modulus of timber beams in torsion tests

The end effect plays an important role in determining where the rotation measuring gauges should be located in a torsion test. A thorough review on the impact of end effect in a torsion test has been conducted, followed by an experimental validation. A close-ranged photogrammetric method using binocular stereo vision technique was employed in this study. The results have indicated that the end effect has a great impact on a region of 1.5 times the cross-sectional depth of the beam from the supports. Therefore, the distance between the gauges and the supports as specified in BS EN 408:2010+A1:2012 for the torsion test setup is not sufficient for the beams with slender cross-sections. This research has also indicated that it is more appropriate to use the depth of the beam as the referencing dimension to specify this required minimum distance.