Behaviour of Glulam and LVL Beams Loaded Perpendicular to the Grain

Compression, Perpendicular to grain, Eurocode 5, Design, Model1 INTRODUCTIONIn most cases, wood behaves very ductile under acompression load perpendicular to the grain. Oncethe elastic limit is passed, only a small load increasecan be measured with increasing deformation. Evenif large deformations occur, a decrease of the load israrely detected.The design model in Eurocode 5 (EN 1995-1-1:2010-12)is based on the work of (Madsen 2001) and further on(Blaß and Görlacher 2004). The load carrying capacityper-pendicular to the grain can be calculated with eq.(1).Fc,90,d≤kc,90·fc,90,d(1)AefAef is an effective contact area calculated with theexisting contact length and a supporting grain lengthup to 30 mm per side. The factor kc,90 depends on thesupport situation and is differentiated between sillsand beams. For sills a value up to kc,90=1.5 and beamsa value up to kc,90=1.75 is possible. Even though a realfailure does not occur, the main focus of the model ison the ultimate limit state (ULS).While the deformation of timber members may beeasily calculated based on stiffness parameters E orG, and the deformations of mechanical connectionsare described by the slip moduli Kseror Ku, timberdesign codes generally do not provide informationregarding deformations in contact areas underloads perpendicular to grain. In consideration ofthe non-linear ductile behaviour and the reacheddeformations, a displacement based design modelseems desirable.Such a model is presented in the following which isderived from load deformation curves of tests. It isshown that the load can be split up in two parts: aneffective compression stress perpendicular to thegrain in the contact area itself and an additionalpart that can be described as the influence of thecontributing grain length. For an overview of differentmodels see (Leijten 2016).