Damage potential reduction of optimally passive-controlled nonlinear structures

Abstract

The use of energy dissipation devices as an earthquake resistant system is an increasing area of practicalapplication worldwide. They are used as seismic protection systems in order to enhance structural per-formance by increasing inherent damping, raising safety, controlling deformations and balancing asym-metric conditions among others, thus reducing ideally the overall damage potential of the structures. Fewcodes have been developed for the analysis and design of these structures and the existing ones are stillevolving. A key parameter that requires special attention is the added damping – reduced shear basedesign relationship due to, in a philosophical sense, seismic protected structures should assure theassumed performance enhancement. A comprehensive study of the added damping – structural strengthrelationship is conducted through three stages. The first stage is focused on nonlinear single degree offreedom systems, the second is extended to nonlinear 2-DOF systems in order to consider the torsionalcondition, and lastly a real eight story frame is analyzed. Structural performance is estimated via fragilitycurves constructed through the Incremental Dynamic Analysis. Damage is estimated through the Parkand Ang index which is composed of two main parameters, the first related to damage caused by ductilitydemand, the second related to structural hysteretic dissipated energy. An ensemble of 42 Chileanaccelerograms recorded at the Mw 8.8 2010 Maule Earthquake scaled to fifteen increasing intensities isconsidered. An optimal plan and height distribution of damping capacities is considered for the 2-DOFsystem and the eight story frame respectively. The Simplified Sequential Search Algorithm is the opti-mization technique implemented. Besides fragility curves, an added damping – strength capacity chartis presented as a decision-making tool. Structural strength reductions should be carefully consideredin order to assure an effective damage potential reduction, especially when dealing with asymmetricstructures.