Wind-induced transmission of low frequency vibrations for a tall multi-storey wood building

Sammanfattning: The building industry accounts for a large part of the world’s carbon dioxide emissions. At the same time the awareness of sustainable construction and production phase has increased and focus has been directed towards the material wood. Likewise, continuing urbanisation requires multi-storey buildings made of wood which brings along certain difficulties and challenges. Due to the low mass of wood, the structural stiffness is less than that of a similar concrete building. On top of that, vibrations that are induced by wind are easily transmitted through the construction. Even if lightweight constructions comply to the present regulations, acoustic comfort is sometimes not met and complaints from residents arise. This thesis investigates if people could be affected by building vibrations and the sound generated by different types of loads, e.g. wind loads. This is done by creating a predictive modelling approach with available prediction tools. The model is not calibrated against any measurements, but for the design of the structure, an example case is used, namely Wood Innovation and Design Centre. This existing structure is seven storeys high and made of wood. The building is designed by Michael Green Architecture and one of their goals is to build a 30-storey or taller wood building. To estimate noise and vibration levels, a finite element model of the aforementioned building is created with 32 storeys. Only wind-induced noise radiated from the enclosing surfaces of a room is analysed. Several parametric tests are performed both to assure the accuracy of the model, and to investigate the most severe sound pressure levels and vibrations occurring in the building. The studies are limited to the low-frequency range from 0 up to 100 Hz. The main conclusion from this thesis is that, for the case under study, the sound pressure level caused by vibrations induced by the wind load itself is not likely to exceed the audible threshold. In an unlikely case with high wind density in frequencies above 50 Hz, i.e. when the excitation force includes large amplitudes at frequencies above 50 Hz, and under certain modelling conditions i.e. fixed connections, could the audible threshold be exceeded. This does not conclude that wind load can not create noise being audible from other types of interactions, such as rattling sound, windows, turbulence due to the building shape, etc. The model in this thesis shows that the recommended vibration levels are exceeded in both the horizontal and the vertical direction, which indicates that people inside of this building probably will be affected by the vibrations. The highest accelerations appear on the top floor for both directions whereas the room placement only is of importance for vibrations in the vertical direction. As this thesis is just touching the possibilities of these modelling tools, more could be explored in the use of acoustic media, submodels and wind load analyses.