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Two multiobjective control strategies are presented and applied to the wind-excited benchmark problem. The first strategy, referred to as the energy-to-peak based controller, deals with a class of 'energy-bounded' excitations, whereas the second strategy, referred to as the peak-to-peak based controller, addresses a class of peak-bounded excitations. Both control strategies are derived by minimizing the sum of weighted peak response quantities with the constraints (or penalties) on the peak values of another set of quantities such as the control resources. Both the state feedback and dynamic output feedback controllers are derived and presented. The design syntheses of these two control strategies are developed and formulated within the framework of linear matrix inequalities (LMIs), so that the LMI toolbox in MATLAB can be used effectively and conveniently. These two control strategies are applied to the wind-excited 76-story benchmark building to demonstrate their applicability and control performances. Simulation results illustrate that the proposed control strategies are viable for civil engineering structures, and their performances are excellent in comparison with that of the linear quadratic Gaussian sample controller. CE Database subject headings: Active control; Structural control; Peak values; Bench marks; Wind loads.

Recently developed [H.sub.[infinity]] control techniques are used to design controllers to suppress the effects of earthquake ground motion on the response of building structures. In particular, controllers are designed to reduce both the interstory drift and the absolute acceleration of selected floors on which sensitive equipment may be installed. Further, the [H.sub.[infinity]] control techniques are extended to include the capability of using acceleration sensors, since direct measurement of floor accelerations is the most reliable and least expensive measurement to make in earthquake engineering applications. Simulation results for a six-story building are used to demonstrate the effectiveness of the control method presented.

Novel low-power or semiactive devices are developed for vibration suppression applications. By manipulating the structural stiffness, the resisting forces generated by the devices are quite large and independent of velocity. Experimental results are presented to demonstrate the feasibility of the devices and to justify the main assumptions used. The critical design issue of device placement is addressed analytically and verified. While much of the development here applies to the case of variable stiffness devices, we focus on resettable devices in which the device behaves like a linear spring. However, at appropriate times, the effective unstretched length of the device is changed—or reset—to extract energy from the vibrating structure. [ABSTRACT FROM AUTHOR]