Under the Transformative Technologies program of Natural Resources Canada, FPInnovations launched the several projects on next generation wood building systems to support the expansion and diversification of wood into new markets. Next generation wood Systems use innovative wood-based materials and systems beyond those defined and addressed in current building codes. As part of this initiative, the serviceability research focuses on addressing issues related to floor and building vibrations, sound insulation and creep by developing provisions and design guidelines to control vibrations and noise in next generation wood buildings.
Cross-laminated-timber (CLT) is a relatively new building product which constitutes is an alternative to concrete in certain applications. Several innovative that incorporate CLT floors and walls have already been designed or built across Canada. Unlike the conventional lightweight joisted wood floor systems, CLT floors are a massive wood slab system generally constructed without the use of joists. There is no design method to determine vibration controlled spans for CLT floors in current codes and standards. This study was conducted from 2008 to 2010 to establish a knowledgebase and database to develop a vibration controlled design method for CLT floors.
CLT floor systems were tested in laboratory with varying construction details including CLT panel thickness, floor spans, type of panel-panel joints, supports, topping and suspended ceilings. The study included performance tests and subjective evaluations to determine the natural frequencies, damping ratios, stiffness indicated by the 1.0 kN static deflections, and human perceptions to the vibration performance of the CLT floors.
Findings from this study indicated that:
fundamental natural frequencies of satisfactory bare CLT floors were above 10Hz;
bare CLT floors had damping ratios around 1%, which is lower than that of the bare conventional lightweight joisted wood floors which had damping ratios around 3%;
type of panel-panel joints used in this study did not noticeably affect the vibration performance of the CLT floors ;
suspended ceiling enhanced the CLT floor damping significantly. Consequently the acceptance of the vibration performance by the evaluators improved or at least did not degrade even the ceiling added additional mass to the floor ;
the wood topping slightly enhanced floor stiffness, therefore the acceptance of the vibration performance by the evaluators improved slightly, or at least did not degrade;
the wood topping and ceiling together noticeably improved or at least did not degrade the vibration acceptance ;
human perception was correlated to the combination of floor stiffness and mass that were measured with the fundamental natural frequencies and 1.0 kN static deflections at the floor centers.
This study formed a knowledgebase and database for the development of vibration controlled design method for CLT floors. Based on this study, a simple design method was developed based on CLT floor stiffness and mass (Hu and Sylvain 2011).