Modal analysis of CLT beams: Measurements and predictive simulations

Cross-laminated timber (CLT) as a prime example of an innovative product within the field of civil engineering has over the recent years attracted attention of the construction industry and engineers around the world. As a natural composite with different orientation of layers in addition to anisotropic properties of wood, CLT can be a challenging material in predictive numerical modelling. This is possibly due to uncertainty in the mechanical behaviour of the material owing to its growing conditions. In addition, timber structures are more sensitive to vibrations and structure-borne sound at low frequencies than conventional concrete based structures. Therefore, a thorough understanding of dynamic characteristics of CLT and accurate predictive models can enhance its potential in the construction industry. This work presents a numerical and an experimental modal analysis of CLT beams within a frequency range relevant for vibrations and structure-borne sound. In the experimental investigation, a series of CLT beams with dimensions 120 120 2000 [mm3], cut from a larger CLT plate, composed of two covering layers of Norway spruce and a mid-layer of Scots pine are studied. Resonant frequencies, bending and torsional modes are utilised for a thorough study of the beams. The results are presented in terms of statistical variation in experimental resonant frequencies. Furthermore, a numerical sensitivity study with respect to variation in the mechanical properties of CLT is presented.