Doctoral project: Connection design for wind induced vibrations in tall timber buildings
How to describe and control wind-induced vibrations in a tall timber building are the new challenging questions that civil engineers and architects ask. Through experiments and development of models, this research project aims to explain the structural dynamic phenomena and propose useful solutions, so that people will feel comfortable and safe in modern wooden skyscrapers rising in our cities.
Doctoral student Pierre Landel Supervisor Andreas Linderholt Assistant supervisor Marie Johansson, RISE Participating organizations Linnaeus University, RISE, Moelven Töreboda Timetable 2017–2022 Subject Mechanical engineering (Department of Mechanical Engineering, Faculty of Technology) Building technology (Department of Building Technology, Faculty of Technology)
More about the project
Wood is a renewable construction material which consumes little energy and has good mechanical properties. It is strong to carry loads and stiff to limit deformation. Moreover, its low density reduces the transport and the foundation costs.
Therefore, the trend of tall timber buildings and the volume of wood in the construction industry increase. The last decade, a dozen buildings above eight storeys have been erected with wood as the main structural material. Mjöstårnet, an 18-storey building in Brumunddal in Norway, is up to now the tallest timber building completed with a height of 84.5 metres. Hundreds of buildings are under construction. Some of them with almost 30 storeys should top the highest trees, i.e. reach above 100 m.
Increased building heights imply tougher requirements, which can be divided in two areas.
On the one hand, they are rules regarding occupants’ safety. I.e., extreme loads (crowd, snow, wind…) and accidental events (fire, explosion, vehicle crash) should not cause irreversible or disproportionate damage.
On the other hand, they are functional thresholds to assure a proper use of an edifice. In that second matter, wind actions must actually be considered.
Slender towers can be designed and built to resist colossal, horizontal loads from violent storms or earthquakes. Still, a moderate breeze can induce annoying sway at the top. To avoid seasick occupants or panic at the top levels, the horizontal accelerations resulting from wind-induced vibrations must be limited; therefore they often tend to govern the structural design.
According to experts, this comfort issue will occur at much lower building height for lighter and more flexible timber structures compared to traditional concrete or steel structures. Mass and stiffness in timber structures are well known and together with damping, they are the three principal parameters ruling the dynamic of structures. However, damping remains unexplored in timber buildings.
To fill the gaps, Linnaeus University and the Research Institutes of Sweden (RISE) initiated a project in 2017 with experiments on large timber constructions, to study and model damping and stiffness of timber connection.