Abstrakti
Impact sound insulation (ISI) is one of the principal technical
parameters often determining the structural layers of timber
intermediate floors. For this reason, in addition to traditional
assessment methods such as laboratory and field measurements,
researchers have developed several strategies to calculate ISI. The aim
of this has been to predict the ISI of timber floors instead of
measurements. Recently, there has also been interest among researchers
in simulating the ISI of timber floors. The method mainly applied in
predictions has been the finite element method (FEM). So far, FEM has
been used to evaluate the ISI of full timber floors mainly at low
frequencies below 250 Hz, which is why full understanding of the
suitability of the method for research or product development purposes
of timber floors have not yet been created.
The main purpose of this research was to study the applicability of a FEM simulation procedure for assessing the ISI of a timber floor. Strictly speaking, the investigations of the study were limited to the evaluation of the normalised impact sound pressure level Ln in a computational setup corresponding to the laboratory measurement where the floor is excited by an ISO standard tapping machine (STM). In order to reach this goal, three separate subproblems had to be solved. Related to the first subproblem, the impact force excitation caused by a STM was experimentally investigated with different timber floors. The observations of the study and the obtained measurement results were used to solve the second sub- problem of the study, which concerned a simulation method for determining the impact force excitation. In the third part, the performance of floor coverings with timber floors was investigated experimentally.
Based on the experimental studies, the impact force excitation caused by the STM on timber floors depends on the type of the floor, and naturally the excitation is also affected by the floor covering. The observed differences between magnitude of the amplitude spectra of the impact force were prominent in the entire frequency range studied, but especially at frequencies above 500 Hz. Experimental studies also showed that the performance of floor coverings depends on the type of the bare floor on which the covering is installed. The measured vibration level reductions of the floor coverings differed both between the timber and concrete mock-up slabs.
It was observed that main reason influencing the discrepancies was the different impact force spectra caused by the STM on different floors. Based on the results, the improvement of ISI of floor coverings should be measured with timber floors when they are intended to be used in timber construction projects.
FEM utilising explicit time integration was selected as the simulation tool to determine the impact force excitation of the STM computationally. The simulation results with a cross-laminated timber (CLT) slab showed that the method was able to predict the excitation caused by the apparatus and explain the differences between the results observed in the measurements. The presented post-processing procedure could be used to determine the point force corresponding to the continuous operation of the STM in the time and frequency domains.
The method for determining the impact force excitation was also applied in the simulations of the normalised impact sound pressure level for a full-scale timber floor in its three different construction stages. Based on the results, the simulation procedure enabled predicting the laboratory measurement result of Ln of a full timber floor and the floor without covering with a 0 to 9 dB accuracy in a situation where the exact material properties of the studied timber floors were not known. Single-number-quantities (SNQs) Ln,w, Ln,w + CI, and Ln,w + CI,50–2500 of the floors were predicted with a 0 to 4 dB accuracy. In case of the bare rib slab, Ln and the SNQs were underestimated by the predictions by 1 to 11 dB, and 4 to 5 dB, respectively. Probable causes for the differences between the simulation and measurement results were uncertain material properties. The applied method can be considered suitable for research and product development use, although the need for further studies and development of the method is obvious.
The main purpose of this research was to study the applicability of a FEM simulation procedure for assessing the ISI of a timber floor. Strictly speaking, the investigations of the study were limited to the evaluation of the normalised impact sound pressure level Ln in a computational setup corresponding to the laboratory measurement where the floor is excited by an ISO standard tapping machine (STM). In order to reach this goal, three separate subproblems had to be solved. Related to the first subproblem, the impact force excitation caused by a STM was experimentally investigated with different timber floors. The observations of the study and the obtained measurement results were used to solve the second sub- problem of the study, which concerned a simulation method for determining the impact force excitation. In the third part, the performance of floor coverings with timber floors was investigated experimentally.
Based on the experimental studies, the impact force excitation caused by the STM on timber floors depends on the type of the floor, and naturally the excitation is also affected by the floor covering. The observed differences between magnitude of the amplitude spectra of the impact force were prominent in the entire frequency range studied, but especially at frequencies above 500 Hz. Experimental studies also showed that the performance of floor coverings depends on the type of the bare floor on which the covering is installed. The measured vibration level reductions of the floor coverings differed both between the timber and concrete mock-up slabs.
It was observed that main reason influencing the discrepancies was the different impact force spectra caused by the STM on different floors. Based on the results, the improvement of ISI of floor coverings should be measured with timber floors when they are intended to be used in timber construction projects.
FEM utilising explicit time integration was selected as the simulation tool to determine the impact force excitation of the STM computationally. The simulation results with a cross-laminated timber (CLT) slab showed that the method was able to predict the excitation caused by the apparatus and explain the differences between the results observed in the measurements. The presented post-processing procedure could be used to determine the point force corresponding to the continuous operation of the STM in the time and frequency domains.
The method for determining the impact force excitation was also applied in the simulations of the normalised impact sound pressure level for a full-scale timber floor in its three different construction stages. Based on the results, the simulation procedure enabled predicting the laboratory measurement result of Ln of a full timber floor and the floor without covering with a 0 to 9 dB accuracy in a situation where the exact material properties of the studied timber floors were not known. Single-number-quantities (SNQs) Ln,w, Ln,w + CI, and Ln,w + CI,50–2500 of the floors were predicted with a 0 to 4 dB accuracy. In case of the bare rib slab, Ln and the SNQs were underestimated by the predictions by 1 to 11 dB, and 4 to 5 dB, respectively. Probable causes for the differences between the simulation and measurement results were uncertain material properties. The applied method can be considered suitable for research and product development use, although the need for further studies and development of the method is obvious.
| Alkuperäiskieli | Englanti |
|---|---|
| Julkaisupaikka | Tampere |
| Kustantaja | Tampere University |
| ISBN (elektroninen) | 978-952-03-3341-6 |
| ISBN (painettu) | 978-952-03-3340-9 |
| Tila | Julkaistu - 2024 |
| OKM-julkaisutyyppi | G5 Artikkeliväitöskirja |
Julkaisusarja
| Nimi | Tampere University Dissertations - Tampereen yliopiston väitöskirjat |
|---|---|
| Vuosikerta | 977 |
| ISSN (painettu) | 2489-9860 |
| ISSN (elektroninen) | 2490-0028 |