Active aerodynamic control of structures

Modern tall buildings and other slender structures are highly susceptible to strong winds, often causing occupant discomfort and in some cases potential structural safety concerns. In this dissertation an innovative active control device is proposed to mitigate the harmful wind effects on tall buildings and structures. This new device termed as Aerodynamic Flap System (AFS) draws important concepts from fluid mechanics and control theory to provide an energy efficient means of reducing the bidirectional (along and across) wind induced motion of tall buildings and other slender structures. AFS is a simple device consisting of two flaps attached on hinges to both the shear layer separation lines of a tall building. The operation of the control flaps is guided by a feedback control algorithm designed to reduce structural vibrations. AFS essentially acts as a vortex generating device and modifies the flow field around the structure. The objective of this dissertation is to present the results of analytical and experimental studies performed to develop design guidelines for the AFS. The dissertation discusses mathematical modeling of the uncontrolled and controlled tall building motion under the influence of wind forces supplemented with results from wind tunnel experiments. Control algorithms required to drive AFS are derived and role of different control parameters is discussed through numerical simulations. Approximate formulations which lead to design guidelines for AFS are also developed. Design example for a typical tall building is presented and practical aspects of AFS implementation are outlined.