| Brace stiffness is generally recognized as important for activating the energy dissipative mechanism of viscous dampers but the exact influence of the brace stiffness on performance of structures remains unclear. In this dissertation, shear-type buildings with Maxwell model-based brace-damper systems are studied with a primary emphasis on the effects of brace stiffness. A single-story building with a viscous damper installed on top of a Chevron brace is first investigated. Closed-form solutions are derived for the simple structure, relating the brace stiffness and damper coefficient to the targeted reduction in response displacement or acceleration. For a given brace stiffness, the mean square of the structural response is minimized to give a set of formulae that will allow the optimal damper coefficient to be deter- mined, assuring the desired performance. The model is subsequently extended to multistory buildings with viscous dampers installed on top of Chevron-braces. For a targeted reduction in the mean square of the interstory drift, floor acceleration or base shear force, the minimum brace stiffness and optimal damper coefficients are obtained through an iterative procedure. The response reduction, which signiffies the improved performance, is achieved by a combination of brace stiffness and viscous damper coefficients, unlike conventional approaches where damper coefficients are typically optimized independent of brace stiffnesses. Characteristics of multi-degree-of-freedom systems are studied using a two-story and ten-story buildings where the effects of brace stiffness on the overall performance of the building can be quantified. |
