Shen, Xiaoxue
(2023)
Transient excitation and response of lightweight timber floors with a heavy impact source.
PhD thesis, University of Liverpool.
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Abstract
Timber floors are widely used in European countries but heavy impacts on floors in lightweight buildings, such as from footsteps in bare feet or children jumping, can cause annoyance and disturbance. Hence, prediction models need to be developed that can estimate sound and vibration transmission from the heavy impact sources that are used to measure impact sound insulation in the laboratory and the field. This thesis uses Finite Element Methods (FEM), analytical models and Transient Statistical Energy Analysis (TSEA) to investigate the structural dynamics of a timber joist floor and its response to an impact from the ISO standard rubber ball. Experimental work has investigated the structural dynamics of the timber joist floor and variation of driving-point mobility, Ydp, over the surface of the floor with different numbers of screws and screw spacings. This has led to a skeleton curve for the prediction of Ydp on the walking surface of the floor. A combination of experimental work and FEM has been used to identify suitable methods of modelling the screw connections as rigid or flexible springs. This showed that by modelling the screws as rigid is valid as a starting point. For flexible springs, both coarse and detailed parametric studies were carried out for the four stiffness K_x,K_y,K_z,K_rz. It was found that K_y was the most important parameter for the transfer mobility in the direction perpendicular to the chipboard and K_x was the most important one for the transfer mobility in the direction perpendicular to the side of the joist. In both cases, K_rz was the second most important parameter. FEM was combined with a Deep Neural Network (DNN) to predict the optimal stiffnesses of the springs. Analytical models were assessed that used periodic, resilient point connections, but these do not appear to be a viable alternative to FEM. Experimental work and FEM model of a rubber ball drop onto a section of timber joist floor were used to validate the transient power input in TSEA. It was found to be reasonable to consider the contact force from the rubber ball as a blocked force. FEM and TSEA models have been implemented to predict the Fast time-weighted maximum vibration level L_(v,Fmax) of the floor, and this showed close agreement with measurements. This thesis shows that the structural dynamics of a timber joist floor can be described with FEM or analytical models and that excitation of the timber walking surface by the ISO rubber ball can be modelled using TSEA.
| Item Type: | Thesis (PhD) |
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| Divisions: | Faculty of Humanities and Social Sciences > School of the Arts |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 22 Aug 2023 15:09 |
| Last Modified: | 22 Aug 2023 15:09 |
| DOI: | 10.17638/03170802 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3170802 |
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