Question

These factors reduce the torsional stiffness D₃₃ as well as the shear stiffness D₈₈ of the corresponding stiffness matrix elements of a surface. Since cross-laminated timber is generally not glued at the narrow side, no shear stresses can be transferred to the narrow sides of the timber. Thus, the stiffness would be overestimated in this case. For this reason, the stiffness must be reduced accordingly.

Some manufacturers provide us with these values when delivering layer structures. They result from internal analysis. The explanation for determining the correction factors is covered in [1]. An analysis of this work has also been included in the Austrian Annex to EN 1995‑1‑1 [2]. The result is shown in Image 02. The ratio of the timber width (a) to the timber thickness (t_i) can be taken from the respective approval. Under "Downloads", you will find an Excel file with the formulas entered.