The advances in height of building structures have magnified their susceptibility to wind-induced vibrations, particularly in typhoon-prone cities. Consequently, considerable efforts have been devoted to the mitigation of wind-induced tall building motions, particularly in the areas of vibration control, wind tunnel high-frequency base balance (HFBB) analysis techniques, and building aerodynamics. However, the mitigation of the wind-induced 3-dimensional (3D) motions of modern tall buildings has been studied by few. Recent evolutions of tall building design have often resulted in significantly nonlinear mode shapes, for which the HFBB analysis techniques commonly adopted for wind tunnel model tests using empirical mode shape correction factors tend to provide substantially larger wind l...[ Read more ]

The advances in height of building structures have magnified their susceptibility to wind-induced vibrations, particularly in typhoon-prone cities. Consequently, considerable efforts have been devoted to the mitigation of wind-induced tall building motions, particularly in the areas of vibration control, wind tunnel high-frequency base balance (HFBB) analysis techniques, and building aerodynamics. However, the mitigation of the wind-induced 3-dimensional (3D) motions of modern tall buildings has been studied by few. Recent evolutions of tall building design have often resulted in significantly nonlinear mode shapes, for which the HFBB analysis techniques commonly adopted for wind tunnel model tests using empirical mode shape correction factors tend to provide substantially larger wind load predictions. The majority of the studies on building aerodynamics have focused primarily on wind load reductions with little consideration given to the practical constraints and the impacts on other engineering and financial aspects. Furthermore, very few studies have focused on the financial implications of response mitigation techniques and consequently there is a lack of vital information to facilitate the cost considerations of full-scale implementations.

A systematic programme of wind tunnel pressure and HFBB studies has been carried out to advance knowledge of the response mitigation techniques, in order to accommodate the current trend of tall building design. A wind-excited benchmark building, which undergoes 3D motions, was first of all developed to provide a standardised means for the study of vibration control and HFBB analyses. Both the acceleration and displacement responses of the benchmark building in the translational and torsional directions were significantly alleviated using a properly-designed bidirectional smart tuned mass damper (STMD), commanded by the linear quadratic regulator control algorithm. The robustness of the STMD to the potential wind-induced aeroelastic effects was then validated by numerically altering the stiffness and damping matrices of the building. A collaborative study was employed to reveal the capital and maintenance costs of the STMD and to develop a cost model for STMD.

A new HFBB analysis, namely the linear-mode-shape (LMS) method, was developed and evaluated to provide more accurate response predictions for buildings with non-ideal mode shapes by establishing a new set of centres at which the translational mode shapes are “linearized”. The LMS method was found to be versatile and superior to provide accurate predictions for a wide range of mode shape exponents. The accuracy of the building responses was further improved by performing the LMS method in the time domain, whereby the modal responses are directly superimposed. The benefits of the LMS method in the time domain were highlighted by the extra reduction in the construction material costs, resulting from an element sizing optimisation.

The understanding of the influence of chamfered and recessed corners on tall building responses was enhanced via a series of wind tunnel HFBB tests and analyses. The recessed corners were found to be more effective than the chamfered corners in reducing both alongwind and crosswind moments, particularly for buildings with shorter aspect ratios and smaller corner modifications. The combined effect of modified corners and additional storeys on the construction cost was then quantified by the derivation of empirical formulae to relate the building responses to the number of storeys. The building configuration that yielded the maximum financial profits was successfully identified through a systematic framework to assess the attributes to the rental incomes of an office building.