Wind-induced dynamic excitation is becoming a governing design action determining size and shape of modern Tall Timber Buildings (TTBs). The wind actions generate dynamic loading, causing discomfort or annoyance for occupants due to the perceived horizontal sway – i.e. vibration serviceability failure. Although some TTBs have been instrumented and measured to estimate their key dynamic properties (natural frequencies and damping), no systematic evaluation of dynamic performance pertinent to wind loading has been performed for the new and evolving construction technology used in TTBs. The DynaTTB project, funded by the Forest Value research program, mixes on site measurements on existing buildings excited by heavy shakers, for identification of the structural system, with laboratory identification of building elements mechanical features coupled with numerical modelling of timber structures. The goal is to identify and quantify the causes of vibration energy dissipation in modern TTBs and provide key elements to FE modelers. The first building, from a list of 8, was modelled and tested at full scale in December 2019. Some results are presented in this paper. Four other buildings will be modelled and tested in spring 2021.
When designing a tall timber building, the accelerations due to wind loads are in many cases decisive. The parameters governing the dynamic behaviour of the building are the structure's stiffness, damping and mass together with the loads. The first two parameters are not well-known during the serviceability limit state of timber structures generally and of timber connections specifically. In this study, dynamical properties of a large glulam truss, a part of the vertical and horizontal structural system in a residential six-storey timber building, are estimated from measurements made in the manufacturing plant. The timber members of the truss are joined with slotted-in steel plates and dowels. Forced vibrational test data are used to extract the dynamical properties. Finite element (FE) models, supported by the experimental results, were developed and simulations, to study the influence of the connection stiffnesses on the total behaviour, were performed. The vibration test results of measurements made on separate structural parts give valuable input to model timber structures and better possibilities to simulate the dynamic behaviour of tall timber buildings as well as the load distribution in wooden structures in the serviceability limit state.
During the last years the interest in multi-storey timber buildings has increased and several medium-to high-rise buildings with light-weight timber structures have been designed and built. Examples of such are the 8-storey building “Limnologen” in Växjö, Sweden, the 9-storey “Stadthouse” in London, UK and the 14-storey building “Treet” in Bergen, Norway. The structures are all light-weight and flexible timber structures which raise questions regarding wind induced vibrations.
This paper will present a finite element-model of a 22 storey building with a glulam-CLT structure. The model will be used to study the effect of different structural properties such as damping, mass and stiffness on the peak acceleration and will be compared to the ISO 10137 vibration criteria for human comfort. The results show that it is crucial to take wind-induced vibrations into account in the design of tall timber buildings.
During the last years the interest in multi-storey timber buildings has increased and several medium-tohigh-rise buildings with light-weight timber structures have been designed and built. Examples of such are the 8-storey building “Limnologen” in Växjö, Sweden, the 9-storey “Stadthouse” in London, UK and the 14-storey building “Treet” in Bergen, Norway. The structures are all light-weight and flexible timber structures which raise questions regarding wind induced vibrations. This paper will present a finite element-model of a 22 storey building with a glulam-CLT structure. The model will be used to study the effect of different structural properties such as damping, mass and stiffness on the peak acceleration and will be compared to the ISO 10137 vibration criteria for human comfort. The results show that it is crucial to take wind-induced vibrations into account in the design of tall timber buildings.
During the last years the interest in multi-storey timber buildings has increased and several medium-to-high-rise buildings with light-weight timber structure have been designed and built. Examples of such are the 8-storey building Limnologen in Växjö, Sweden, the 9- storey Stadthaus in London, UK and being constructed at the moment, the 14-storey building Treet in Bergen, Norway. These are all light-weight and flexible structures which raise questions regarding the wind induced vibrations. For the building in Norway, the calculated vibration properties of the top floor are on the limit of being acceptable according to the ISO 101371 vibration criteria for human comfort. This paper will give a review of building systems for medium-to-high-rise timber buildings. Measured vibration properties for some medium-to-high-rise timber buildings will also be presented. These data have been used for calculating the peak acceleration values for two example buildings for comparison with the ISO standards. An analysis of the acceleration levels for a building with double the height has also been performed showing that designing for wind induced vibrations in higher timber buildings is going to be very important and that more research into this area is needed.
