Impact of Different Lamellae Materials on Vibrations in CLT Panels - A numerical study of concrete, air or elastomer materials
(2024) In TVSM-5000 VSMM01 20241Structural Mechanics
Department of Construction Sciences
- Abstract
- Timber structures are increasingly growing in importance and utilization. A contributing factor to this trend is the introduction of cross-laminated timber (CLT). CLT is an engineered wood product comprising layers of wood made up of multiple boards, alternately referred to as "lamellae". Each layer is positioned perpendicular to the next and bonded together with adhesives. CLT is mostly utilized in floor or wall panels.
Timber structures offer more advantages in terms of sustainability and climate change compared to conventional concrete buildings. However, they are more sensitive to dynamic loading, necessitating the need to improve the design of multi-story wood buildings to reduce vibration levels and low-frequency structure-borne... (More) - Timber structures are increasingly growing in importance and utilization. A contributing factor to this trend is the introduction of cross-laminated timber (CLT). CLT is an engineered wood product comprising layers of wood made up of multiple boards, alternately referred to as "lamellae". Each layer is positioned perpendicular to the next and bonded together with adhesives. CLT is mostly utilized in floor or wall panels.
Timber structures offer more advantages in terms of sustainability and climate change compared to conventional concrete buildings. However, they are more sensitive to dynamic loading, necessitating the need to improve the design of multi-story wood buildings to reduce vibration levels and low-frequency structure-borne sound levels. Previous studies show potential to integrate viscoelastic materials in CLT panels to achieve this. This dissertation further explores this potential by examining the effects of exchanging lamellae with alternative materials other than conventional spruce. These alternative materials include concrete and two types of elastomer. Additionally, the possibility to remove certain lamellae without significantly impacting the dynamic behavior of the panel was evaluated.
The predictions of vibrations were accomplished through the utilization of the commercial FE software Abaqus. In Abaqus, two finite element models were constructed, named "Layered model" and "Lamellae model". The Layered model compromised of layers excluding the individual lamellae, used for obtaining spruce material parameters that accurately represent reality. The Lamellae model consisted of layers including the individual lamellae, used to determine the impact of different lamellae material.
The material parameters for spruce were calibrated using Newton optimization on the most influential parameters. Several calibrations were performed, with the most accurate calibration displaying a normalized relative frequency difference (NRFD) of less than 1%.
When studying the impact of different lamellae material two CLT panels were used, consisting of different dimensions and lay-ups. The results were evaluated mainly in root mean square (RMS) and 1/3 octave bands.
Significant reductions in the level of vibration can be achieved by replacing spruce lamellae with concrete, particularly when the concrete lamellae are located close to the outermost parts of the panels. Replacing 2% of the spruce lamellae with concrete indicated approximately 60% reduction in the vibration levels.
Furthermore, air cavities in CLT panels can be modeled as an empty space because modeling air as an acoustic medium in comparison to as an empty space indicated no significant difference in vibration level.
Moreover, a potential was found to remove spruce lamellae in CLT panels giving up to 20% material reduction without significantly amplifying the vibration levels.
Additionally, exchanging spruce lamellae to elastomer demonstrated reductions in vibration level at certain frequency intervals and amplifications in others. However, there were certain configurations, which showed significant reduction in vibration level over continuous frequency intervals. It demonstrates potential to place elastomer lamellae in a way that is favorable for specific frequency intervals. For example, replacing 14% of the spruce lamellae with elastomer showed approximately 50% reduction in the vibration levels. (Less) - Popular Abstract
- Timber structures are increasingly growing in importance and utilization. A contributing factor to this trend is the introduction of cross-laminated timber (CLT). CLT can be more advantageous in terms of sustainability and climate change compared to concrete. However, CLT is more sensitive to dynamic loading, necessitating the need to improve the dynamic performance of CLT panels. Significant improvement in dynamic performance of CLT panels was shown to be obtained by exchanging lamellae from traditional spruce to concrete or elastomers. Additionally, a potential to remove 20 percent of the spruce lamellae without significantly amplifying the vibration levels was found.
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9162383
- author
- Johansson, Sam and Ung, Khuong An
- supervisor
-
- Peter Persson LU
- Annie Bohman LU
- organization
- alternative title
- Inverkan av olika lamellmaterial på vibrationer i KL- träpaneler – En numerisk studie på betong, hålrum eller elastomer material
- course
- VSMM01 20241
- year
- 2024
- type
- H3 - Professional qualifications (4 Years - )
- subject
- publication/series
- TVSM-5000
- report number
- TVSM-5270
- ISSN
- 0281-6679
- language
- English
- id
- 9162383
- alternative location
- https://www.byggmek.lth.se/english/publications/tvsm-5000-present-2014/
- date added to LUP
- 2024-06-25 11:03:28
- date last changed
- 2024-06-25 11:27:35
@misc{9162383,
abstract = {{Timber structures are increasingly growing in importance and utilization. A contributing factor to this trend is the introduction of cross-laminated timber (CLT). CLT is an engineered wood product comprising layers of wood made up of multiple boards, alternately referred to as "lamellae". Each layer is positioned perpendicular to the next and bonded together with adhesives. CLT is mostly utilized in floor or wall panels.
Timber structures offer more advantages in terms of sustainability and climate change compared to conventional concrete buildings. However, they are more sensitive to dynamic loading, necessitating the need to improve the design of multi-story wood buildings to reduce vibration levels and low-frequency structure-borne sound levels. Previous studies show potential to integrate viscoelastic materials in CLT panels to achieve this. This dissertation further explores this potential by examining the effects of exchanging lamellae with alternative materials other than conventional spruce. These alternative materials include concrete and two types of elastomer. Additionally, the possibility to remove certain lamellae without significantly impacting the dynamic behavior of the panel was evaluated.
The predictions of vibrations were accomplished through the utilization of the commercial FE software Abaqus. In Abaqus, two finite element models were constructed, named "Layered model" and "Lamellae model". The Layered model compromised of layers excluding the individual lamellae, used for obtaining spruce material parameters that accurately represent reality. The Lamellae model consisted of layers including the individual lamellae, used to determine the impact of different lamellae material.
The material parameters for spruce were calibrated using Newton optimization on the most influential parameters. Several calibrations were performed, with the most accurate calibration displaying a normalized relative frequency difference (NRFD) of less than 1%.
When studying the impact of different lamellae material two CLT panels were used, consisting of different dimensions and lay-ups. The results were evaluated mainly in root mean square (RMS) and 1/3 octave bands.
Significant reductions in the level of vibration can be achieved by replacing spruce lamellae with concrete, particularly when the concrete lamellae are located close to the outermost parts of the panels. Replacing 2% of the spruce lamellae with concrete indicated approximately 60% reduction in the vibration levels.
Furthermore, air cavities in CLT panels can be modeled as an empty space because modeling air as an acoustic medium in comparison to as an empty space indicated no significant difference in vibration level.
Moreover, a potential was found to remove spruce lamellae in CLT panels giving up to 20% material reduction without significantly amplifying the vibration levels.
Additionally, exchanging spruce lamellae to elastomer demonstrated reductions in vibration level at certain frequency intervals and amplifications in others. However, there were certain configurations, which showed significant reduction in vibration level over continuous frequency intervals. It demonstrates potential to place elastomer lamellae in a way that is favorable for specific frequency intervals. For example, replacing 14% of the spruce lamellae with elastomer showed approximately 50% reduction in the vibration levels.}},
author = {{Johansson, Sam and Ung, Khuong An}},
issn = {{0281-6679}},
language = {{eng}},
note = {{Student Paper}},
series = {{TVSM-5000}},
title = {{Impact of Different Lamellae Materials on Vibrations in CLT Panels - A numerical study of concrete, air or elastomer materials}},
year = {{2024}},
}