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Vibrations in timber floors: Dynamic properties and human perception
Linnaeus University, Faculty of Technology, Department of Building and Energy Technology.
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Kalmar, Växjö: Linnaeus University Press, 2014. , 64 p.
Series
Linnaeus University Dissertations, 195/2014
Keyword [en]
wooden floor, timber floor, vibration, design criteria, damping, frequency, questionnaire, field test, socio-vibrational survey, vibration annoyance, vibration disturbance
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
URN: urn:nbn:se:lnu:diva-39305ISBN: 978-91-87925-23-8 (print)OAI: oai:DiVA.org:lnu-39305DiVA: diva2:782513
Public defence
2014-11-07, N1017, hus N, Växjö, 10:00 (English)
Opponent
Supervisors
Available from: 2015-01-21 Created: 2015-01-21 Last updated: 2015-01-21Bibliographically approved
List of papers
1. Vibrations of wooden floor elements on supporting steel framework
Open this publication in new window or tab >>Vibrations of wooden floor elements on supporting steel framework
2004 (English)In: Proceedings of the 8th World Conference on Timber Engineering, Lahti, Finland, 2004, 2004Conference paper, Published paper (Refereed)
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-39298 (URN)
Conference
8th World Conference on Timber Engineering, Lahti, Finland, 2004
Available from: 2015-01-21 Created: 2015-01-21 Last updated: 2015-01-21Bibliographically approved
2. Dynamic properties of a sawn timber floor element with high transverse bending stiffness
Open this publication in new window or tab >>Dynamic properties of a sawn timber floor element with high transverse bending stiffness
2006 (English)In: Building Acoustics, ISSN 1351-010X, Vol. 13, no 4, 295-310 p.Article in journal (Refereed) Published
Abstract [en]

A novel wooden floor system for blocks of flats, schools and office buildings where long spansare required is investigated. The floor system aims at high stiffness and good vibration performance. In the longitudinal, main load-bearing direction the floor system works as a truss with flanges of longitudinally oriented timber members and web diagonals of transversely oriented members. In the transverse direction the web diagonals work as beams. A 2.4  4.8 m floor element with a total height of 260 mm is examined. Laboratory tests as well as static FE calculations show that the bending stiffness in the transverse direction is of the order of one fourth of the bending stiffness in the main direction. The torsional stiffness is however low. The dynamic properties, i.e. natural frequencies and modes of vibration were evaluated using laboratory tests and FE calculations. In general, laboratory tests and FE calculations were in good agreement. As the study shows promising results, further development and testing are proposed. A test floor is planned in which the transversely oriented wooden members will be replaced by thinwebbed beams of wood and hardboard. In future, the floor will be examined with respect to acoustic properties.

Place, publisher, year, edition, pages
MULTI-SCIENCE PUBLISHING CO. LTD.5 Wates Way, Brentwood, Essex CM15 9TB, United Kingdom, 2006
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:vxu:diva-4534 (URN)
Available from: 2007-05-11 Created: 2007-05-11 Last updated: 2015-01-21Bibliographically approved
3. Effect of flexible supports on vibration performance of timber floors
Open this publication in new window or tab >>Effect of flexible supports on vibration performance of timber floors
2012 (English)In: Euronoise, Prague 2012, 10-13 June, 2012: Proceedings, European Acoustics Association (EAA), 2012, 214-219 p.Conference paper, Published paper (Refereed)
Abstract [en]

In residential multi-storey buildings of timber it is of great impor-tance to reduce the flanking transmission of noise. Some buildingsystemsdothisbyinstallingavibration-dampingelasticinterlayer,Sylomerror Sylodynr, in the junction between the support andthefloorstructure.Thisinterlayeralsoimprovesthefloorvibrationperformance by adding damping to the structure. In the presentwork the vibration performance of a floor with such interlayershas been investigated both in laboratory and field tests. A pre-fabricated timber floor element was tested in laboratory on rigidsupports and on supports with four different types of interlayers.Theresultsarecomparedwithin situtests on a copy of the samefloorelement.Theeffectonvibrationperformancei.e.frequencies,damping ratio and mode shapes is studied. A comparison of theinsitutestandthetestwithelasticinterlayerinlaboratoryshowsthatthe dampingin situis approximately three times higher than on asingle floor element in the lab. This indicates that the dampinginsituisaffectedbethesurroundingbuildingstructure.Theachieveddamping ratio ishighly dependent onthe mode shapes. Mode sha-pes that have high mode shape coefficients along the edges wherethe interlayer material is located, result in higher modal dampingratios. The impulse velocity response, that is used to evaluatethe vibration performance and rate experienced annoyance in thedesign of wooden joist floors, seems to be reduced when adding elastic layers at the supports.

Place, publisher, year, edition, pages
European Acoustics Association (EAA), 2012
Series
Euronoise proceedings, ISSN 2226-5147
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-28050 (URN)978-80-01-05013-2 (ISBN)
Conference
Ninth European Conference on Noise Control (Euronoise), Prague, 10-13 June, 2012
Available from: 2013-08-12 Created: 2013-08-12 Last updated: 2016-10-03Bibliographically approved
4. Vibration properties of a timber floor assessed in laboratory and during construction
Open this publication in new window or tab >>Vibration properties of a timber floor assessed in laboratory and during construction
2015 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 82, 44-54 p.Article in journal (Refereed) Published
Abstract [en]

Natural frequencies, damping ratios and mode shapes of a prefabricated timber floor element have been assessed experimentally in laboratory with different boundary conditions and in situ (in field) at different stages of construction. In laboratory the change in modal parameters was studied with free-free boundary conditions and simply supported on two sides. Three different simply supported tests with changes in boundary conditions were carried out; the floor placed on the support without any fastening or interlayer between support and floor, the floor screwed to the supports and the floor placed on an elastic interlayer between support and floor. The in situ tests were carried out first on the single floor element and then on the entire floor of the room into which the floor element was built in. The damping ratio of the floor increased from 1% to 3% when simply supported in laboratory to approximately 5% when placed upon a polyurethane interlayer (Sylodyn) in situ, and to approximately 6% when fully integrated in the building. Thus the in situ conditions have considerable influence on the damping and the values assessed are very high in comparison with damping values suggested in design codes. Regarding natural frequencies it was concluded that the major change in these occur as the floor element is coupled to the adjacent elements and when partitions are built in the studied room, the largest effect is on those modes of vibration that are largely constrained in their movement.

Keyword
Timber floor Wooden floor Vibration Damping Frequency Mode shape Modal analysis
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-37983 (URN)10.1016/j.engstruct.2014.10.019 (DOI)000346545900005 ()2-s2.0-84910634710 (Scopus ID)
Available from: 2014-11-03 Created: 2014-11-03 Last updated: 2017-12-05Bibliographically approved
5. Vibration performance of lightweight floors in multifamily houses: Resident survey and field measurement
Open this publication in new window or tab >>Vibration performance of lightweight floors in multifamily houses: Resident survey and field measurement
(English)In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910XArticle in journal (Refereed) Submitted
National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-39300 (URN)
Available from: 2015-01-21 Created: 2015-01-21 Last updated: 2017-10-19
6. Psycho-vibratory evaluation of timber floors: Towards the determination of design indicators of vibration acceptability and vibration annoyance
Open this publication in new window or tab >>Psycho-vibratory evaluation of timber floors: Towards the determination of design indicators of vibration acceptability and vibration annoyance
Show others...
2015 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 340, 383-408 p.Article in journal (Refereed) Published
Abstract [en]

In timber housing constructions, vibrations can be a nuisance for inhabitants. Notably, the vibrational response of wooden floor systems is an issue in need of being dealt with more adequately in the designing of such buildings. Studies addressing human response to vibrations are needed in order to be able to better estimate what level of vibrations in dwellings can be seen as acceptable. In the present study, measurements on five different wooden floors were performed in a laboratory environment at two locations in Sweden (SP in Växjö and LU in Lund). Acceleration measurements were carried out while a person either was walking on a particular floor or was seated in a chair placed there as the test leader was walking on the floor. These participants filled out a questionnaire regarding their perception and experiencing of the vibrations in question. Independently of the subjective tests, several static and dynamic characteristics of the floors were determined through measurements. The ultimate aim was to develop indicators of human response to floor vibrations, specifically those regarding vibration acceptability and vibration annoyance, their being drawn based on relationships between the questionnaire responses obtained and the parameter values determined on the basis of the measurements carried out. To that end, use was made of multilevel regression. Although the sample of floors tested was small, certain clear trends could be noted. The first eigenfrequency (calculated in accordance with Eurocode 5) and Hu and Chui׳s criterion (calculated from measured quantities) proved to be the best indicators of vibration annoyance, and the Maximum Transient Vibration Value (computed on the basis of the accelerations experienced by the test subjects) to be the best indicator of vibration acceptability.

National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-39303 (URN)10.1016/j.jsv.2014.12.001 (DOI)
Available from: 2015-01-21 Created: 2015-01-21 Last updated: 2017-12-05Bibliographically approved

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