Design uncertainty in long span mass timber floors: proposed band-beam solution

Abstract

The low relative density of timber compared to other building materials (concrete and steel) increases its sensitivity to low frequency footfall vibrations. Coupled with the scarcity of experimental data on in-situ floor vibration performance, shorter clear spans (~8 m) and excessive panel thicknesses are often prescribed for mass timber floors. This study combines in-situ performance testing of an existing mass timber floor under a conventional 5.5 m span supported by glulam with a conceptual cross-laminated timber band-beam. The existing floor performance met those of a high frequency floor (>10 Hz natural frequency, 2.93% damping ratio). Sensitivity testing indicated damping ratios and floor classifications (low or high frequency) can greatly impact response factor calculations. A conceptual floor design was implemented by replacing the hardwood glulam with thinner, laboratory-tested band-beams. The numerical results indicated a change in the floor classification and an increase in response factor. Further experimental investigations can help determine the optimal band-beam design.