Impact of natural variability in structural properties on vibrations of CLT floors

This paper studies the uncertainty in modal properties and pedestrian-induced acceleration response of a multi-panel CLT floor due to natural variability in structural parameters: timber material properties, inter-panel connections and damping ratio. A sensitivity analysis showed that the timber density, longitudinal modulus of elasticity and shear modulus had the greatest impact on variability of natural frequencies and modal masses, while variability in inter-panel connections had a negligible influence. Therefore, the uncertainty analysis of acceleration response considered the timber density, longitudinal modulus of elasticity, the shear modulus and the floor damping ratio as random variables. On the other hand, the pedestrian loading was modelled deterministically, according to the widely used CCIP-016 design guideline. Two large sets of response simulations were established. In so called “non-resonant” case, the walking frequency was fixed in all simulations, and the resonance was expected just sporadically. In “resonant” case, the walking frequency was adjusted in each simulation to hit the floor resonance. The “non-resonant” results demonstrated that the guideline-based deterministic response had a very low probability of occurrence. In contrast, it aligned reasonably well with the “resonant” results, indicating that the guideline provides rational vibration levels only for a likely occurrence of resonance.