Influence of laminate direction and glue area on in-plane shear modulus of cross-laminated timber
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Influence of laminate direction and glue area on in‑plane shear modulus of cross‑laminated timber Jonas Turesson1 · Zahra Sharifi1 · Sven Berg1 · Mats Ekevad1 Received: 16 August 2020 / Accepted: 18 November 2020 © The Author(s) 2020 OPEN
Abstract The use of cross-laminated timber (CLT) in constructing tall buildings has increased. So, it has become crucial to get a higher in-plane stiffness in CLT panels. One way of increasing the shear modulus, G, for CLT panels can be by alternating the layers to other angles than the traditional 0° and 90°. The diagonal compression test can be used to measure the shear stiffness from which G is calculated. A general equation for calculating the G value for the CLT panels tested in the diagonal compression test was established and verified by tests, finite element simulations and external data. The equation was created from finite element simulations of full-scale CLT walls. By this equation, the influence on the G value was a factor of 2.8 and 2.0 by alternating the main laminate direction of the mid layer from the traditional 90° to 45° and 30°, respectively. From practical tests, these increases were measured to 2.9 and 1.8, respectively. Another influence on the G value was studied by the reduction of the glue area between the layers. It was shown that the pattern of the contact area was more important than the size of the contact area. Keywords Cross-laminated timber · Diagonal compression test · Laminate direction · Shear modulus · Finite elements · Glue
1 Introduction A cross-laminated timber (CLT) panel is a building component used for a variety of purposes such as walls, floors, roofs and beams [1]. CLT is a panel built by boards in a cross wise arrangement in a specific number of layers. Normally an odd number of layers 3, 5 and 7 is used, but also CLT with an even number of layers 2, 4 and 6 is possible. Boards used to construct CLT panels are based on strength class and dimension. The material and size of the boards will determine the properties of the CLT panel [2]. One important property of the CLT panels is the inplane shear stiffness characterised by the shear modulus, G. This is not interchangeable with the shear modulus of wood because shearing of a CLT panel does not necessarily mean shearing of the wood. G is important for CLT walls
if they are used as shear walls to resist lateral movements of buildings. Lateral (shear) stiffness is important, and it is necessary to have sufficient lateral stiffness, especially for tall wooden buildings [3]. Several parameters affect the shear stiffness in a CLT panel. Important parameters are constituent board dimensions, board strength class, possible gaps between boards, gluing method and gluing area and the number of layers that build the CLT panel [4]. Traditional CLT panels use cross wise laminate directions, meaning directions 0°, 90°, 0° and so on as directions of the laminates. Two possible gluing methods are used for CLT panels. One is to glue only the flat sides of the boards, and the other one is to glue
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