Wind-induced vibrations in high-rise buildings

Abstract: Buildings are getting taller due to increased urbanisation and densification of cities. More advanced construction methods and the desire to construct impressive buildings is also supporting the trend. Due to their inherent slenderness resulting in low eigenfrequencies, these buildings are susceptible to wind-induced vibrations which can be highly disturbing for occupants. Already barely perceivable acceleration levels within the low-frequency range relevant to whole-body vibrations can cause nausea and discomfort, while high acceleration levels can cause alarm and fear amongst the occupants. The thesis summarises acceptable acceleration levels in high-rise buildings (here referred to as buildings over 200 m in height) stated in different building codes and previous work on the subject. Equations for estimating acceleration in tall buildings in an early design stage are formulated. Accelerations of a high-rise building subjected to wind-loads are evaluated using a full numerical model and one reduced with Ritz-vectors and the results are compared. The thesis focusses on wind-load dynamics in early stages of the design process, with an intent to give an indication of the dynamic properties of a building. Finally some actions to reduce vibrations are discussed.