Effect of birch in CLT elements : An investigation of how introducing birch effects the strength properties of CLT elements

Sammanfattning: In this thesis, material properties for a CLT element have been examined with regard to the structure of theelement and its content of different types of wood. The focus has been on how Birch affects the properties,since its properties in shear are much better compared to the commonly used pine and spruce.Calculations have been made in python script within the Rhino 6 software and its Grasshopper plugin.Grasshopper basically works with coding but with a visual interface that is very user friendly. This programhas been used because of its parametric structure which makes changes in the structure very simple andthe whole model changes with the changes in parameters.The basis for the survey has been the following parameters:• Number of layers within the KL element• Widths of lamellae• Thicknesses of lamellae• Material properties of Birch, Pine and Spruce• Quotas between Birch, Pine and SpruceThe results show that the shear stiffness of the CLT-element increases with the amount of birch. The value ofthe G-moduli, however, does not only depend on the amount but the positioning as well. The shear stiffnessis the greatest when the birch is placed closest to the middle of the element.The conclusion made is that further investigation of the practical and economical aspects are required to makean informed decision about whether the use of birch or increased board width is the most efficient method ofimproving the shear stiffness of CLT.