Cost-based design and performance of supplemental viscous dampers attached to non-consecutive floors

Abstract

The cost-based optimal height-wise distributions of viscous dampers in multistory structures is investigated in this paper emphasizing applications for which the dampers are attached to the main structure in such a way that they are subjected to the motion of a given floor relative to that of a non-consecutive floor (e.g., two or three floors apart) rather than, as usual, to the relative motion between consecutive floors. It is shown under simplifying assumptions that, for a given level of energy dissipation, damping systems in which (linear or nonlinear) dampers are connected every nc floor levels reduce damper force demands nc times with respect to dampers attached to consecutive floor levels. Since the cost of the damping system is directly related to these forces, implementation of non-consecutive connectivity schemes could lead, therefore, to significant economic benefits. To investigate this trends under more realistic modeling assumptions, a height-wise damper distribution optimization scheme that explicitly considers cost associated with damper forces is developed. Seismic excitation is modeled as a stochastic process, and response statistics are obtained through state-space analysis. Different objective functions related to damper forces are adopted, whereas structural performance is incorporated in the design as a constraint, requiring that a specific level of vibration suppression be achieved through the damper implementation. The design of a supplemental viscous damping system for an actual Chilean 26-storey building considering an excitation that is compatible with the regional seismic hazard is examined as illustrative example. Comparisons between consecutive and non-consecutive bracing schemes demonstrate that dampers connected across multiple floors contribute to considerable reduction for the damper force demand.