Passive and active control of civil structures under dynamic wind loads
Abstract
A procedure for designing an active tuned mass damper for vibration control in tall buildings subject to wind loads is presented. The building motions are modeled by the first mode of the response, and it is assumed that the excitation is white noise. For the assumed control law the controller gains that minimize the variance of the rooftop displacement are derived in closed-form. Two examples of tall buildings are studied to illustrate the active damper design. The same examples are then studied as multiple degree-of-freedom systems subject to non-white excitation which better simulates the wind. Results on the reduction of the dynamic response and control effectiveness of the active damper designs are presented and discussed. This analysis may also be used in designing active mass dampers for other structures like cooling towers or chimneys, provided the first mode of the response dominates the motion. Next a method for the multiple-objective design of controllers for tall buildings is described. It is assumed that there are constraints on the design, in terms of limiting certain displacements, velocities, or accelerations to be within prescribed values and in terms of the maximum control force available. The solution process involves posing the search for a controller as a problem of constrained optimization for which the Lagrange multipliers are determined by an ellipsoid algorithm. It is noted that the design problem is one of optimal weight selection in the LQG setting. Active mass dampers are designed for the building examples considered earlier using this technique. Results on the performance of the designs are presented and the behavior of the controlled structure is discussed. The generality of the current procedure enables it to be applied directly to other kinds of structures, like bridges, shell-like domes, cooling towers, or tall chimneys, under earthquake or wind loads and using either active mass dampers, active tendon control, or active base isolation as appropriate.
Degree
Ph.D.
Advisors
Yang, Purdue University.
Subject Area
Aerospace materials|Civil engineering|Mechanics
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