Vibrations in timber floors Dynamic properties and human perception

Abstract: Springiness and vibrations of timber floors are familiar to many as a ‘live’ feelwhen walking on them, especially if living in single family housing with timberframework. Since the building regulations in Sweden changed to performancedependentrequirements in 1994 the use of timber in multifamily housing hasincreased. New timber building systems have been developed and increasedbearing capacity of floors has made it possible to build with longer spans. Thelow mass of timber floors makes them more sensitive to dynamic loading byhuman activities, such as walking, running and jumping, compared to heavyfloors e.g. concrete floors. To improve vibration performance it is possible tochange the structural properties of the floors by increasing mass, stiffness ordamping properties. The most practicable solution is to increase the stiffness.Improved damping is also highly effective, but is difficult estimate and designaccurately since it originates from many sources in the finished building. In thepresent thesis the effects on dynamic properties from increased stiffnesstransverse to the load bearing direction of a floor have been assessed from testsin laboratory. The effect on dynamic performance of a timber floor fromelastic/damping interlayers (polyurethane elastomers) installed in the junctionsbetween walls and floors have been assessed in laboratory and in situ. Also thechange in dynamic properties of an in situ floor has been investigated atdifferent stages of construction and compared with results from laboratory tests.The present criteria for design of timber floors with respect to vibrationperformance were developed at a time when timber floors were mainly used insingle-family housing. The traditional timber joist floors differ in structuralbehaviour from the new types of floors developed recently. The experiencedvibration annoyance by residents in single- and multifamily housing differs asthe source of vibration disturbance and those who become disturbed aredifferent. The changed conditions give cause for a review of present designcriteria. A laboratory and field study on vibration performance was conductedwith questionnaires and dynamic performance measurements. The subjectiveand objective results were correlated and indicators for vibration acceptabilityand annoyance were assessed and new vibration performance criteria andvibration performance classes were suggested.