Reduced order modelling of elastomeric vibration isolators in dynamic substructuring

Dynamic substructuring is often employed to reduce the size of numerical models for structural dynamic analysis. In this paper, we discuss how elastomeric vibration isolators can be modelled within the framework of dynamic substructuring in order to obtain accurate and efficient reduced order models. For several reasons, it is beneficial to divide a structure containing elastomeric isolators into substructures at the interfaces between elastomers and surrounding parts of the structure. Therefore, we consider the elastomeric isolators as reduced coupling elements in the connections of substructure models. The coupling elements are established by reducing the number of degrees of freedom of 3D finite element models of elastomers. The main purpose of the studies presented in the paper is to evaluate the performance of different reduction method when applied to elastomer models. In addition, the effects of modelling features such as rotational coupling and frequency-dependent material properties of elastomeric isolators are investigated. A model of a wooden building structure with elastomeric isolators is used as an example case, considering steady-state dynamic analysis in the low-frequency range. The results and discussions presented in the paper provide guidance for reduced order modelling of elastomeric isolators in dynamic substructuring

A multi-level model correlation approach for low-frequency vibration transmission in wood structures

The main challenge in predicting structure-borne sound in wood buildings is to accurately model the vibration transmission between the source and the receiving room. Large variations in model parameters make it difficult to predict absolute vibration levels and to make conclusions regarding the relative effects of different designs. A step towards establishing reliable models is to investigate the possibilities and limitations of using deterministic methods, which requires correlations between simulations and measurements. In this paper, we present a multi-level model correlation approach for low-frequency vibration transmission in wood buildings. We apply the proposed approach to a scaled-size experimental structure representing a part of a two-storey wood building, and we evaluate the results for frequencies up to 100 Hz. We perform correlations between simulations and measurements four different levels: structural components (viz. beams and boards), planar structures (viz. floor, ceiling and walls), room structures and the complete structure. The results indicate that the dynamic behaviour of the experimental structure was to a great extent captured by the developed model. Based on the observations made in the multi-level correlations, we discuss important model parameters and propose modelling guidelines. We conclude that it is possible to employ deterministic methods in order to simulate the low-frequency vibration transmission in wood buildings provided that measurement data for calibration purposes are available. The developed numerical model can be used as a reference model for investigations on the effects of variations and uncertainties in the modelling

Effect of modelling the air in rooms on the prediction of vibration transmission in cross-laminated timber buildings

Timber buildings are intrinsically lightweight and hence can be susceptible to low-frequency vibrations and structure-borne noise. So, within the development of technical solutions for mitigating unwanted vibrations and noise, accurate and computationally efficient numerical models are considered to be of great value. Such models should take into account all physical phenomena that are relevant for achieving adequate accuracy in predictions, while not being overly detailed so that the computational efficiency is impaired. In this paper, the necessity of modelling the enclosed air in room volumes of buildings made of cross-laminated timber, with respect to the prediction of vibration transmission, is investigated. Coupled structural-acoustic finite element analysis is employed for an example building structure. It is found that modelling the air in the receiver room, i.e. in the room where the vibration response is evaluated, has a marked effect on the vibration transmission between panels

Vibroacoustic performance of multi-storey buildings : A comparison of lightweight and heavy structures in the early design phase

With the construction sector being responsible for about 40% of the energy and material use, the sector has a great responsibility for lowering the consumption if we are to succeed in our global pursuit for the green transition. However, buildings must still comply with the demands of users. For long-span, openspace lightweight, multi-storey buildings, this provides a potential risk related to annoyance caused by vibration and structure borne noise. This paper addresses the multilateral effects of building typology in terms of the vibroacoustic performance and the environmental impact. Based on an automized digital framework, multistorey buildings made of cross-laminated timber and/or concrete are modelled and compared. Finite-element analysis is used for the dynamic structural analysis, and the architectural design tool Rhino is used for material take-offs and visualisation. The aim of the paper is to provide insight into the advantages and disadvantages of different building typologies to be used for informed decision making in the early stages of design

Early assessment of the vibroacoustic performance of large lightweight buildings

As part of the green transition, a current trend in the construction sector is to utilize more wood and lightweight composites, aiming at a reduction of the embodied energy in buildings. At the same time, with a focus on circularity and reuse, large-span structures are preferable, since they provide more flexibility for future uses of the building. The mix of large spans and lightweight structures pose a risk in terms of increased vibration levels. Hence, assessment of the vibroacoustic performance of a building is necessary in the early design stage to guide the designers towards useful solutions. This paper presents a computational framework for such assessment. While the framework is based on the combination of advanced digital tools for architectural design and rigorous finite-element modelling of the structure, a simple-to-use spreadsheet interface allows the non-experienced used to perform analysis. To provide an example, a small building made of cross-laminated timber has been analysed regarding its steady-state response to time-harmonic excitation on a floor. The paper demonstrates how representative acceleration levels can be achieved at a low computational cost