DESIGN OF A MEGA-SUB-CONTROLLED BUILDING SYSTEM UNDER STOCHASTIC WINDLOADS

Vibration control of high-rise buildings under wind loads with applica tion of the mega-sub-control method is studied in this paper. A buildi ng with a mega-sub-configuration consists of two major structural comp onents - a megastructure as the main structural frame and several sub- structures for residential and/or commercial usage. The authors have p reviously proposed a 'mega-sub-control method' in which the sub-struct ures are designed to serve as vibration control dampers. The control o bjective is to suppress certain critical building responses such as in ter-story drifts of the mega-structure for the purpose of structural s afety and acceleration response of the sub-structures for the purpose of protecting contents and improving human comfort. The feasibility of this method has been explored by the authors in previous publications . In this study, the procedure of optimally designing dynamic paramete rs of a mega-sub-controlled building under stochastic wind loads is de veloped, together with two possible structural configurations which pr ovide a mega-sub-control mechanism. The mega-structure of a mega-sub-b uilding is modeled as a cantilever beam to retain the dominant bending mode characteristics of high-rise buildings, and the sub-structure as a shear building to retain the shear mode. The fluctuating wind speed is modeled as a non-white random process in both time and space domai ns. The power spectral density (PSD) of critical building responses is obtained using the random vibration theory. The mean square value (MS V) of those responses, as functions of the dynamic parameters includin g the stiffness and damping ratio of the sub-structures, are evaluated from their PSD by numerical integration in the frequency domain. The optimal values of the dynamic parameters are determined by minimizing the MSV of certain critical building responses. An example building is used to demonstrate the design procedure and the numerical simulation of the response quantities in the time domain is carried out to verif y the MSV of the building responses obtained from the random vibration theory in the frequency domain. The results show that the proposed de sign procedure is suitable to apply to a mega-sub-building with differ ent sub-structural configurations. The MSV obtained from the random vi bration theory in the frequency domain and from the numerical simulati on in the time domain exhibit an excellent agreement. It is also found that the mega-sub-control method is robust in the sense that slight c hange in the dynamic parameters affects the building's performance ver y little. With the design procedure developed, and the corresponding f avorable building response demonstrated, this paper has enhanced the f easibility of application of the mega-sub-control method to actual hig h-rise buildings for wind vibration suppression. (C) 1997 Elsevier Sci ence Ltd.