Acceleration Response Spectrum for Predicting Lightweight Timber Floor Vibration Subjected to Crowd Bouncing Excitation

The vibration serviceability of lightweight timber floors under crowd-induced excitation presents significant challenges due to their high stiffness/weight ratio and susceptibility to human-induced vibrations. Existing design codes lack specific methods for predicting dynamic responses under crowd bouncing loads, particularly when considering crowd-structure interaction (CSI). This study proposes a response spectrum model that considers CSI and crowd synchronization effects to predict timber floor vibrations. First, stochastic analysis reveals that CSI significantly changes the mean dynamic properties of the system and introduces significant uncertainty. A response reduction factor (RRF) is introduced to quantify crowd synchronization, showing an exponential decrease with increasing crowd size and demonstrating insensitivity to structural parameters. Integrating these effects, a design-oriented response spectrum model is proposed, incorporating stochastic human parameters and validated through field tests. Predictions at the 75% confidence level conservatively exceed measured data, confirming the reliability of the model for vibration serviceability design of timber floors under crowd bouncing loads. The proposed model provides a practical tool for vibration serviceability design of timber floors.