Distribution of large-earthquake input energy in viscous damped outrigger structures

Abstract

This article provides an analytical framework to assess the distribution of seismic energy in outrigger structures equipped with viscous dampers. The principle of damped outriggers for seismic control applications lies on the assumption that the total earthquake energy will be absorbed by the dampers, as the rest of the structure remains elastic during the seismic event. Nevertheless, under large or severe earthquake-induced motion, some plastic hinges or failures may be produced in the structure before the dampers are able to dissipate the total input energy. Therefore, hysteretic behaviour of the host structure need to be evaluated along the dampers’ performance in order to determine how the earthquake input energy is distributed by all the components. In order to effectively assess the inter-dependency between structural properties of tall buildings equipped with damped outriggers and ground motion characteristics of large earthquakes in the control performance, a parametric study -considering building predominant period, position of the outrigger, damping coefficient, and stiffness ratio core/perimeter columns- on the nonlinear behaviour of two building models –fixed and with viscous damper - is examined under two large-earthquake records. The results show that the use of passive control –viscous dampers- gradually reduce the potential of damage in the building structure as they reduce both the input and the hysteretic energy demands, and thus eventually extending the capabilities of the damped outrigger to large-earthquake induced motion control.