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©2012 Civil-Comp Ltd |
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A. Sjöström1, O. Flodén1, K. Persson1, P.H. Kirkegaard3, D. Bard2 and J. Negreira2
1Division of Structural Mechanics, 2Division of Engineering Acoustics,
Lund Institute of Technology, Lund University, Sweden
3Department of Civil Engineering, Aalborg University, Denmark
Keywords: finite element method, junction, vibrations, buildings, multi-storey, lightweight, wood.
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In multi-storey buildings, the use of lightweight material has many advantages. The low weight, the low energy consumption and the sustainability of the material are some attractive benefits from using lightweight materials. Compared with heavier structures (i.e. concrete) the challenge in constructing a building compliant with building codes concerning the propagation of sound and vibrations within the structure is a challenge. Focusing on junctions in a multi-storey lightweight building, a modular finite element model is developed to be used for the analyses of vibration transmission in lightweight buildings exposed to different types of loads.
This paper discusses the applicability of the finite element method in the simulation of two types of screwed and glued junctions typically found inside lightweight wooden floors as well as the behaviour of junctions at floor supports where the influence of an elastomer in junctions between floor, walls and ceilings was studied.
In the study of the T-junctions, the influence of the use of glue in lightweight junctions was investigated using measurements and compared with the finite element simulations. It was observed in measurements that in the single plate case, the glue did not have much of an influence on the lower frequencies. The slight differences observed in the measurements between the glued and non-glued case for a single plate may be caused by the anisotropy of the spruce beam and its different properties in the types of junction and not of the glue itself. This can be the result of, for instance, knots or also because of the damping properties of the glue.
The parameter study undertaken on the glue showed that the type of glue does not influence to a great extent the response of the structure at least not when considering the structural damping in the glue. It was observed that the attenuation is much higher when a discontinuity is present then in the case of a continuous plate when calculating the attenuation from the simulated frequency sweeps. It can be concluded that the differences in attenuation are not a consequence of the properties of the glue, particularly the structural damping.
An extensive investigation regarding the flanking transmission when introducing an elastomer in a lightweight junction was also carried out. It was shown that regardless of the orientation of the load bearing beams in the floor and ceiling or the placement of the elastomer, the reduction of acceleration magnitudes within the blocks of the elastomer is very effective.
It was also shown using a parameter study that a variation of the modulus of elasticity of the elastomer does not greatly influence the vibration transmission through the junction.
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