Optimal reduction of seismic floor acceleration response using viscous dampers connecting non-consecutive floor levels

Abstract

Several studies have explored the optimization of the seismic response of structures with viscous dampers. Most of these studies define the optimal performance of the system in terms of the inter-story drift response, either exclusively or in combination with other quantities such as floor acceleration, energy dissipation, or cost-related quantities. However, the optimal reduction of floor accelerations exclusively (i.e., without considering any other response quantity) has not been exhaustively analyzed. The location of dampers connecting non-consecutive floor levels in buildings is a popular technique used in Chile for improving the efficiency of the supplemental dampers in stiff structures. The objective of the study presented in this paper is to analyze the height-wise distributions of viscous dampers that minimize the seismic floor accelerations in multistory buildings, with emphasis on damper bracings that connect non-consecutive floor levels. Uniform and non-uniform solutions were explored, and suboptimal solutions that minimize the damping constants ? were defined. The seismic demand was modelled as a non-stationary gaussian process. Two types of excitations with different frequency content were considered. The structures were modeled as shear-type, linear elastic models (1 DOF per story). Optimization algorithms were applied to find the optimal solutions. The objective function was defined in terms of the stochastic response of the structures. The second moment of the floor acceleration response was obtained using the Explicit Time Domain Method. It was found that configurations with dampers spanning 2 or 3 floor levels achieve the same damping ratio as configurations with dampers at every story, but with smaller values of ?. In some cases, the optimal response reduction was achieved with less damping than the maximum possible damping level that is feasible in practice, particularly in long period structures on firm soil. It was also found that when dampers connect non-consecutive floor levels the optimal response reductions and the damping ratios are similar to those achieved when dampers connect consecutive floor levels.