Acceleration response modification factors for nonstructural components attached to inelastic moment‐resisting frame structures

Abstract

A statistical analysis of the peak acceleration demands for nonstructural components (NSCs) supported on a variety of stiff and flexible inelastic regular moment-resisting frame structures with periods from 0.3 to 3.0 s exposed to 40 far-field ground motions is presented. Peak component acceleration (PCA) demands were quantified based on the floor response spectrum (FRS) method without considering dynamic interaction effects. This study evaluated the main factors that influence the amplification or decrease of FRS values caused by inelasticity in the primary structure in three distinct spectral regions namely long-period, fundamental-period, and short-period region. The amplification or decrease of peak elastic acceleration demands depends on the location of the NSC in the supporting structure, periods of the component and building, damping ratio of the component, and level of inelasticity of the supporting structure. While FRS values at the initial modal periods of the supporting structure are reduced due to inelastic action in the primary structure, the region between the modal periods experiences an increase in PCA demands. A parameter denoted as acceleration response modification factor (R acc ) was proposed to quantify this reduction/increase in PCA demands.focused on both accurately estimating the acceleration demands and also on developing methods for seismic performance assessment. The ATC-58 document presents an overview of the seismic performance assessment of nonstructural systems namely identifying the damage to NSCs, developing probabilistic relationships between damage states and engineering demand parameters (i.e. NSC damage fragility functions), and evaluating the consequences of the predicted damage [7,8]. New formulae that have been proposed to estimate the peak component acceleration (PCA) demands to improve the current code provisions consider the buildings to respond elastically or practically elastic [9, 10]. However, many types of conventional structures are designed to experience significant inelastic deformations when subjected to severe levels of earthquake ground motions. This inelastic behaviour of the supporting structure will influence the demands on NSCs significantly [11,12].Current seismic code provisions [13-15] utilize engineering demand parameters for NSCs that are not directly linked to the nonlinear dynamic response of actual buildings in which the components are located. The effect of inelasticity of the component is addressed through the component response modification factor (R p ), but not the inelastic action of the building. Recent research efforts on developing approximate but rational methods for estimating the nonlinear response of NSCs in buildings have used conventional strength-reduction factors developed for single-degree-of-freedom (SDOF) structures to scale the elastic component demands to obtain the inelastic component behaviour [16]. However, the validity of the use of the same strength-reduction factors that are used in building designs for an entire elastic...

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