Reduction of Wind Induced Motion Utilizing a Tuned Sloshing Damper

Serviceability of buildings is affected by excessive acceleration experienced at the top floors in wind storms that may cause discomfort to the occupants. To ensure functional performance of tall buildings it is important to keep the frequency of objectionable motion levels below the discomfort threshold. This paper addresses a new approach that facilitates mitigation of wind induced motion of buildings utilizing tuned sloshing dampers. First, a theoretical background of the fluid sloshing system is given, which is followed by modeling of sloshing fluid and structural systems. An example of a tall building equipped with a tuned sloshing damper is presented to illustrate the effectiveness of such devices in mitigating structural motion. Finally, a brief discussion of the potential for practical applications is presented. INTRODUCTION The current trend of buildings with ever increasing heights and lights facades has led to the construction of relatively flexible structures possessing quite low damping. The resulting sensitivity of these buildings to dynamic excitation by wind has increased. Besides various failure possibilities, cladding and partition damage, serviceability of a building is an important design criteria. The serviceability of a building is affected by excessive acceleration experienced at the top floors in wind storms that may cause discomfort to the building occupants. Therefore, to ensure functional performance of tall buildings it is important to keep the frequency of objectionable motion levels below the discomfort threshold. Various possibilities exist to achieve this goal, the global design modifications presented in Table 1 range from considering alternative structural systems to aerodynamic modification. Further details on the effectiveness of each alternative are discussed in Kareem (1983). The use of tuned mass dampers and viscoelastic dampers is gaining wide acceptance in building industry as evidenced by recent implementation of these devices in tail buildings and other flexible structures (e.g., McNamara, 1977, Wiesner, 1986, Keel, 1987 and Kitamura, et al. 1988). Recent studies have demonstrated that sloshing fluid in a container if properly tuned acts like a tuned mass damper in reducing structural response (Sun & Kareem, 1986; Kareem & Sun, 1987; Modi & Welt, 1987; Fujino, et al., 1988; Tamura et al., 1988). Earlier studies, though not particularly focussed on their application to engineering structures, also concluded that for a proper selection of design parameters, containers partially filled with fluids serve as good vibration dampers (Sayar & Baumgarten, 1982). Dampers utilizing liquid motions have been utilized successfully in satellites and on ocean vessels (Bhuta & Kov~, 1966, Harris & Crede, 1987). Most of * Professor and Director, Structural Aerodynamics and Ocean System Modeling Laboratory, University of Houston, Houston, TX 77204-4791. 0167-6105/90/$03.50 © 1990---Elsevier Science Publishers B.V.