Vibration attenuation in cross-laminated timber–steel composite floors using loose sand as a passive damping mechanism

Lightweight timber-based floor systems are known to be susceptible to poor vibration serviceability. When hybridized with steel, the intrinsic low damping of steel may affect the overall vibration performance of the floor system. Common measures adopted to enhance vibration serviceability include stiffness enhancement, span reduction, and damping improvement. This study focuses on the latter, and loose sand is investigated as a simple passive damping mechanism in hybrid cross-laminated timber (CLT)-steel composite floors via modal tests and walking-induced acceleration measurements. The results indicated enhancements in the damping values of composite floor modules with beams filled with loose sand over those without sand, with an additional 2 % damping on average. Damping ratios peaked at 7 % in floors with loose sand, resulting in considerable reductions in their acceleration metrics. Due to added weight, the damped composite floors experienced a slight drop in fundamental frequencies by about 5 % on average, but their mode shapes were unaffected. Overall, the study showed that incorporating loose sand can enhance the vibration performance of hybrid CLT–steel composite floors.