VIBRATION CONTROL OF TALL BUILDINGS UNDER SEISMIC AND WIND LOADS

A procedure for the design of a second-order dynamic controller is pre sented. The proposed method is applied to the control. of structures u nder earthquake and wind excitations. The controller gains are determi ned by minimizing the root-mean-square value of the response parameter of interest for the structure, assuming that the excitation is Gaussi an white noise. Three examples of structures (of which two are assumed to be subjected to the N-S component of the 1940 El Centro earthquake and one is assumed to be excited by wind loads) are considered to ill ustrate the design technique, In the first of the earthquake engineeri ng applications, the controller is used for active base isolation of a building modeled as a shear frame, while in the second, it is used to develop an active mass damper for a three-dimensional building with e ccentric axes of inertia and rotation (and consequently coupled longit udinal, lateral, and torsional motions). The wind engineering applicat ion is the design of an active mass damper for a high-rise building mo deled as a planar frame subjected to wind loads. Numerical results for the examples reveal that the actively controlled base-isolation syste m with velocity feedback has better performance than that with either acceleration or displacement feedback. Complete feedback (i.e., feedba ck using position, velocity, and acceleration) was used for the active mass damper designs, and the controller was seen td be quite effectiv e in reducing displacement and acceleration levels for both the three- dimensional building (with-various eccentric locations of the axes of rotation and inertia) and for the planar frame. For all examples studi ed the active control systems were observed to perform better than the ir passive counterparts. Comments on the performance and control effec tiveness of these designs and closed-loop-system behavior are made.