Design of CLT Beams with Large Finger Joints at Different Angles

A new finger joint profile, developed for LFJ in CLTbeams, is presented. To determine the reductionof the bending strength resulting from LFJ, testswith straight CLT beams with and without LFJ wereperformed. Based on the test results a reductionfactor of (1 – 0.30) = 0.70 is proposed for the bendingstrength of LFJ in straight beams. The factor includesthe nominal reduction resulting from the finger jointprofile and further reduction due to productiontolerances and manufacturing processes.For LFJ in CLT beams jointed under varying anglesthe influence of the cutting angle α on the bendingstrength was determined from tests with doublepitched CLT beams and CLT frame corners. The resultsof tests show that the bending strength of LFJ in CLTis far less dependent on the cutting angle than thebending strength of LFJ in glulam. For LFJ subjectedto opening moments the reduction of the bendingstrength for angles up to 25° is less than 50 %. For LFJsubjected to closing moments even a greater bendingstrength was found than for straight beams. Based onthe test results a design proposal for LFJ in CLT beamsis made, taking into account the strength reductionresulting from the LFJ and the influence of the cuttingangle α.