Encouraged by our recent project at Bishop’s Stortford College that utilised a folded CLT roof we are carrying out research with the University of Cambridge that looks into one of the standard CLT connections – a half-lap between panels.

A comparison between Finite Element modelling, laboratory testing of full-scale panels and analytical solutions is carried out to help us understand the rotational stiffness properties of a simply screwed half-lap and how it depends on a number of variables. Of particular importance is the Particle Image Velocimetry (PIV) technique used to obtain and post-process results from the laboratory tests.

A half-lap joint is tested in a four-point bend test whilst PIV takes two high resolution images, before and after a load is applied. Bespoke computer software then compares the two images and is able to track the movement of material to sub-pixel accuracy. This technique was used to display the deformed shape of the screw and help identify areas of high stress in the CLT.

Images courtesy CUED (Allan McRobie and Ewan Macpherson)