| 1. |
- Bolmsvik, Åsa, 1975-, et al.
(författare)
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Model calibration of wooden structure assemblies : using EMA and FEA
- 2014
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Ingår i: World Conference on Timber Engineering (WCTE), Quebec City, 10-14 August, 2014.
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Konferensbidrag (refereegranskat)abstract
- To predict and possibly, when needed to fulfil regularizations or other requirements, change the design to lower the impact sound transmission in light weight buildings prior to building, dynamically representative calculation models of assemblies are out most important. The quality of such models depends on the descriptions of the components themselves but also of the representation of the junction connecting the building components together. The material properties of commonly used components have a documented spread in literature. Therefore, to validate junction models, the dynamics of the assembly components at hand have to be known. Here, the dynamic properties of a number of component candidates are measured using hammer excited vibrational tests. Some of the components are selected to build up wooden assemblies which are evaluated both when they are screwed together and when they are screwed and glued together. The focus is here on achieving representative finite element models of the junctions between the building parts composing the assemblies.
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| 2. |
- Bolmsvik, Åsa, 1975-, et al.
(författare)
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Damping Assessment of Light Wooden Assembly With and Without Damping Material
- 2013
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Ingår i: Engineering structures. - : Elsevier BV. - 0141-0296 .- 1873-7323. ; 49, s. 434-447
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Tidskriftsartikel (refereegranskat)abstract
- Damping elastomers are often used in lightweight wooden constructions and are believed to have good sound insulating effects. In the present study the influence on the structural behaviour by using elastomer damping material (Sylomer®) in the joints, with particular respect to footsteps and floor vibrations, has been investigated. A full scale wooden mock-up was assembled with two different joint configurations and studied under free-free boundary conditions. In the first configuration, the joints between the floor and underlying walls were screwed together. In the second configuration the floor was resting free on top of ribs of elastomer damping material, equivalent to normal building practice when this material is used. Both configurations were analysed and evaluated using experimental modal analysis, in the frequency interval 10-115 Hz. The relative (viscous) damping ratios of the modes were found to be on average 1.2% for the screwed configuration and 2.1% for the configuration with elastomer damping material in the joints. The damping was found to vary significantly between modes in the elastomer case. It was found that at low frequencies damping was high for modes with large motion on the edge where the elastomer material was. At higher frequencies (above approx. 40 Hz), however, the damping for this configuration decreased. This is believed to be caused by a vibration isolation effect of the elastomer, decoupling the floor from the walls at higher frequencies. To assess the differences in vibration levels between the two configurations, mean acceleration levels of well spread points on the different building parts where computed and evaluated. It was found that above approximately 70 Hz, the mean vibration level in the elastomer configuration was significantly lower than for the screwed configuration. Below 70 Hz, however, for many frequencies the mean vibration level for the elastomer configuration was significantly higher than for the screwed configuration (as should be expected in vibration isolation). Problems with springiness and footsteps are due to loads in the frequency range of 10 to 50 Hz, this could indicate that elastomers, used as in the present study, could worsen these types of problems, although improving higher frequency acoustic performance.
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| 3. |
- Bolmsvik, Åsa, 1975-, et al.
(författare)
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Damping elastomers for wooden constructions : Dynamic properties
- 2015
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Ingår i: Wood Material Science & Engineering. - : Taylor & Francis. - 1748-0272 .- 1748-0280. ; 10:3, s. 245-255
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Tidskriftsartikel (refereegranskat)abstract
- Elastomers are commonly used to decrease the sound transmission between apartments in timber framed houses. Inprevious studies, different types of connections have been evaluated. However, the frequency dependent dynamic propertiesin different directions of a connection including elastomers are not fully investigated yet. Previous studies have actuallyshown that elastomers cause the vibrations to increase in the direction perpendicular to the applied load within the lowfrequency span. The properties of the elastomers are needed in order to model the dynamic behaviour and thereby be ableto predict sound and vibration transmissions in wooden houses in the future. With known properties, the elastomerconnections can be modelled using springs and dashpots. In this study, dynamic experiments have been made on elastomerstrips half embedded. The test setup has been subjected to various loads using an electromagnetic shaker. The responseshave been measured and evaluated using modal analysis. With different loads, non-linear characteristics of the elastomers’behaviour have been obtained. The elastomers have also been tested quasi-statically, to obtain a load-deflection curve.Finally, the estimated properties of the elastomers have been included in an FE model using springs and the analyticalresults are compared with the experimental results.
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| 4. |
- Bolmsvik, Åsa, 1975-, et al.
(författare)
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FE modeling of a lightweight structure with different junctions
- 2012
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Ingår i: Proceedings of EURONOISE 2012. - : European Acoustics Association. - 9788001050132 ; , s. 162-167
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Konferensbidrag (refereegranskat)abstract
- In lightweight structures it is common to use damping material in junctions to decrease sound transmission. In field measurements, the damping properties of the structure are easily overestimated due to the omnipresent energy losses to the surroundings. Thus, reliable estimates of structural properties cannot be guaranteed. Vibrational tests were done on a full scale wooden construction, consisting of a floor and supporting beams, representing walls, to investigate the effect of different junctions. Totally seven different setups were made using the same building components. In one setup the floor and the walls were screwed together, in five setups different elastomers was positioned between the floor and the walls and in the last setup the floor was resting free on top of the walls. A shaker, with pseudorandom excitation, was used for the excitation of the structure and accelerometers were used for response measurements. The effect of the junction was investigated by studying the acceleration levels in the edge part of the floor-wall junction in different directions. Modal data, extracted from test data using experimental modal analysis, form input and validation data for the following finite element (FE) analysis. Two FE models; modeling one elastomer and the screwed setup, are used for the studies. The aim was to study if the eigenmodes rendering the acceleration levels are similar in test and in analysis, using common material properties. The results from correlation between test and analytical results show that the material properties of the wood need to be known better; more sophisticated models are needed to fully simulate the dynamic behavior of the structure. Anyhow, with the used properties the mode shapes are captured fairly well in the lower frequencies. Furthermore, the experiment shows that the damping properties of the junction material have a major influence on the behavior of the structure.
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| 5. |
- Bolmsvik, Åsa, 1975-, et al.
(författare)
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FE Modelling of Light Weight Wooden Assemblies : parameter study and comparison between analyses and experiments
- 2014
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Ingår i: Engineering structures. - : Elsevier. - 0141-0296 .- 1873-7323. ; 73, s. 125-142
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Tidskriftsartikel (refereegranskat)abstract
- A finite element (FE) analysis of a model representing a mock-up structure previously investigated experimentally is investigated in this study. The aim is to make a correlation and calibration between test and analysis of the full scale wooden structure; both eigenmodes and acceleration levels are compared. Large scatter is found in material properties used for light weight wooden structures in literature. In this study, a parameter evaluation is therefore made to show how different properties influence the dynamic behaviour of the structure. It is shown that the wood beam material properties influence the behaviour of the light weight wooden structure FE model most.Two types of junctions are modelled and evaluated; a tied connection is used to simulate screwed junctions and spring/dashpot elements are used to represent elastomer junctions between the floor and the walls. The springs and dashpots used to model the elastomer in the junction work well in the bearing direction but need to be improved to obtain correct rotational stiffness, shear motion and friction. There are still many unknown parameters in a complex wooden structure that remain to be investigated. However, the results presented in this paper add data to be used for FE modelling of a complex wooden structure.
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| 6. |
- Bolmsvik, Åsa, 1975-, et al.
(författare)
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FE modeling of wooden building assemblies
- 2010
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Ingår i: InterNoise 2010-Lisbon Portugal 13-16 June. ; , s. 1-10
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Konferensbidrag (refereegranskat)abstract
- Residential timber framed buildings have in some cases received complaints from inhabitants due to structure-borne sound at low frequencies, even if the building meets the regulations with respect to impact sound quality. This paper describes FE-analyses to evaluate the test setups of a building assembly and to prepare for the full-scale experimental modal analysis planned. By modal analysis, the dynamic properties of a structure, such as eigen modes and damping characteristics, can be extracted. The test assembly consists of prefabricated wall and floor/roof timber elements. Different assembly and joining methods as well as building element are used. The eigen modes and damping differs between the assemblies investigated which influence the dynamic response in the lower frequencies. The results are carefully evaluated and planned measurements are discussed.
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| 7. |
- Bolmsvik, Åsa, 1975-, et al.
(författare)
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Stiffness and damping evaluation of Elastomers in different setups
- 2015
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Ingår i: Proceedings of the Internoise 2015 conference. - : Society of Experimental Mechanics (SEM).
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Konferensbidrag (refereegranskat)abstract
- In timber buildings, elastomers are commonly used to decrease the sound transmission between apartments. Detailed properties of the elastomers are needed in order to model them in a correct yet computational efficient manner. In earlier studies, dynamic experiments have been made on elastomer strips half embedded. However, the sidewise effects need to be further evaluated. In this study, the elastomers are evaluated quasi-statically in different directions, having continuous as well as intermittent distributions, being plane supported or half embedded. An FE-model has been developed using data stemming from the quasi-static tests together with damping estimates stemming from vibrational tests.
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| 8. |
- Bolmsvik, Åsa, 1975-
(författare)
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Structural-acoustic analysis of wall-to-floor joints in timber-framed housing
- 2009
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Even though a building meets the regulations with respect to impact sound, structures with wooden frames may receive complaints from the inhabitants due to structure-borne sound in the lower frequencies. In this thesis measuring methods that are more precise than the traditional measuring methods have been used to see if they could give a better knowledge about flanking transmission in the low frequencies in timber-framed structures. The measuring results have been compared to FE models of a complete room. By comparing the non-traditional measurement results with the results from the FE model a straight forward comparison could be made.Two field measurements have been made within the scope of this thesis. In the first field measurement a two-storey house with four apartments was studied. A traditional tapping machine was used as a source, and an accelerometer measured the responses in the apartment below. This study showed differences in acceleration levels on the surrounding surfaces in the room below the source. The non-bearing apartment-separating wall was the surface that had the largest acceleration levels. In the second field measurement several accelerometers were used simultaneously to measure the responses. With the help of experimental modal analysis and by measuring at several points at the same time the operational deflection shapes of all surrounding surfaces in the reception room could be captured. In this measurement a shaker was used as a source, so that the applied load could be measured the whole time. The load had constant level containing all frequencies within the studied frequency range. Simultaneously, a microphone was used and the acceleration levels in the surrounding surfaces could be compared to the sound pressure in the room. The measurements showed, not surprisingly, that at the frequency where the largest sound pressure was found all surrounding surfaces had acceleration peaks.An FE analysis of the room from the second field measurement has been made. The analysis shows that by using a load similar to the load used in the experiments the velocity level of the responses are in the same range both in the analysis and in the experiments. It also shows that damping has a large influence and that the damping needs to be studied further to be able to use the model as a prediction tool for flanking transmission.However, even though the results from the measurements and the analysis have some deviations, a great deal can be learned about the phenomenon of flanking transmission of timber-framed structures by using the proposed methods.
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| 9. |
- Bolmsvik, Åsa, 1975-
(författare)
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Structural-acoustic vibrations in wooden assemblies : Experimental modal analysis and finite element modelling
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This doctoral thesis concerns flanking transmission in light weight, wooden multi-storey buildings within the low frequency, primarily 20-120 Hz. The overall aim is to investigate how the finite element method can contribute in the design phase to evaluate different junctions regarding flanking transmission.Two field measurements of accelerations in light weight wooden buildings have been evaluated. In these, two sources; a stepping machine, and an electrodynamic shaker, were used. The shaker was shown to give more detailed information. However, since a light weight structure in field exhibit energy losses to surrounding building parts, reliable damping estimates were difficult to obtain.In addition, two laboratory measurements were made. These were evaluated using experimental modal analysis, giving the eigenmodes and the damping of the structures. The damping for these particular structures varies significantly with frequency, especially when an elastomer is used in the floor-wall junction. The overall damping is also higher when elastomers are used in the floor-wall junction in comparison to a screwed junction. By analysing the eigenmodes, using the modal assurance criterion, of the same structure with two types of junctions it was concluded that the modes become significantly different. Thereby the overall behavior differs.Several finite element models representing both the field and laboratory test setups have been made. The junctions between the building blocks in the models have been modeled using tie or springs and dashpots. Visual observation and the modal assurance criterion show that there is more rotational stiffness in the test structures than in the models.The findings in this doctoral thesis add understanding to how modern joints in wooden constructions can be represented by FE modelling. They will contribute in developing FE models that can be used to see the acoustic effects prior to building an entire house. However, further research is still needed.
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| 10. |
- Bolmsvik, Åsa, 1975-
(författare)
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Structural Vibrations of Wooden House Walls
- 2006
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Ingår i: Journal of BUILDING ACOUSTICS. - : MULTI-SCIENCE PUBLISHING CO. LTD.. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- The flanking transmission between apartments due to a structure borne source is studied. The apartments studied were two-storey houses with a wooden framework. Acoustic measurements are often made in new built apartments to make sure that they fulfil the building regulations. Traditional measurements give no information about the contribution of the surrounding walls to the sound transmission. This paper describes a method of measuring flanking transmission. The acceleration levels on the receiving parts in the apartment below the source are studied. Thereby the contribution to the sound pressure in the room from each flanking part can be distinguished.
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