Experimental Modal Analysis and variability assessment in Cross-laminated Timber

Experimental Modal Analysis (EMA) plays a crucial role in understanding the dynamic responses of structures to vibration by extracting their modal parameters such as natural frequencies and modal damping and vibration modes. These parameters are essential for assessing structural performance and identifying potential vulnerabilities. As the construction industry embraces sustainable materials, Cross-laminated Timber (CLT) has become a sustainable alternative to traditional materials like reinforced concrete and steel. However, the inherent variability of wood, resulting from factors such as growth conditions, fibre structure, and moisture content, introduces significant fluctuations in the dynamic response of CLT. This variability presents challenges in the broader application of CLT in construction. Despite its increasing use in multistory buildings, a comprehensive assessment of its vibrational characteristics remains incomplete. This study addresses this gap by identifying the dispersion in CLT's transfer functions and modal parameters through EMA. A CLT slab was divided into 24 nominally identical beam-like substructures, composed of outer layers of Norway spruce and a middle layer of Scots pine. EMA was performed in a broad frequency spectrum along three principal directions, revealing notable variability in resonance frequencies, modal damping, and vibration transfer functions. The study also examines the distinct characteristics of the bending, torsional, and axial vibration modes, providing deeper insights into the variability between the different modes. The findings of this article contribute to a more refined understanding of the dynamic properties of CLT and their associated variability.