Vibration of suspended solid-timber slabs without intermediate support: assessment for human comfort

Mass timber flooring is an effective use of low-grade timber. However, lightweight, unsupported, timber slabs are particularly susceptible to vibrations in the frequency range that causes discomfort to occupants. The purpose of this investigation is to determine whether panelised solid timber slabs vibrate within acceptable standards for human comfort. The first three natural frequencies and associated mode shapes of five 4.4 m × 0.28 m × 0.09 m nail laminated, MGP10 Radiata Pine test panels were investigated using accelerometers to validate and calibrate a finite element model in Ansys Workbench. The finite element model was then extended to study three slabs spanning 4.4 m, with widths in the range 4.2–8.4 m. Marginally acceptable levels were achieved by the thinnest slab tested (90 mm), however with increased slab depth, the recommended limits are easily satisfied. These conclusions are shown likely to be conservative when furnishings and fittings are accounted for. As results are dominated by the stiff dimension, conclusions can be extrapolated to wider slabs, thus this represents a viable method of construction for slabs of any width spanning 4.4 m.