Experimental and numerical investigations on vibration performance of mass timber slab floors with floating concrete toppings

Mass timber floor systems face serviceability challenges such as deflection, sound insulation, and vibration due to their relatively light weight and low bending stiffness. Floating concrete topping is often applied to improve acoustic performance and fire resistance, though its impact on vibration performance is less understood. The current Canadian design standard CSA O86-24 suggests ignoring the effect of concrete topping when applying the vibration-controlled span equation if its area density is less than twice of the bare cross laminated timber (CLT) floor area density. Floating concrete toppings typically don’t necessitate mechanical fasteners, although limited tests have shown partial composite behavior. This study experimentally investigated the vibration performance and dynamic properties of mass timber slab floors with floating concrete toppings, examining two dowel laminated timber (DLT) floors with varying thicknesses, spans, concrete topping thicknesses, floor assemblies, and boundary conditions. Effective bending stiffness was derived from experimental data as inputs for fundamental natural frequency calculation. Additionally, two finite element models were developed for modal analysis of mass timber floors with floating concrete toppings. Results demonstrated that the floating concrete topping could significantly enhance the floor system’s vibration performance, improving an unacceptable bare timber floor to acceptable levels. However, its impact on the fundamental natural frequency depends in the thickness of the concrete topping and details of floating floor assemblies. Composite action between the concrete topping and timber slab existed even without mechanical fasteners, though the degree of this action varied across different assemblies. Accurate modeling of such floor systems can be achieved with careful consideration of input of material properties and partial composite action factors. • The vibration performance of mass timber slabs with floating concrete toppings was investigated experimentally. • Partial composite action behavior was observed with varying composite efficiency. • Recommendations for modal analysis of mass timber floors with floating concrete toppings were provided .