Construction of elastic spectra for high damping

Abstract

Construction of a site-specific elastic response spectrum is a well-defined and common procedure to describe earthquake action. Such a spectrum is usually defined for 5% damping ratio, which is a suitable value for most conventional buildings. In recent times, design of buildings with Passive Energy Dissipation systems has become usual. A common feature of such systems is an enhancement of structural damping, typically over 20%. A robust and efficient verification procedure for this type of systems is the capacity spectrum method using equivalent properties and elastic response spectra, conveniently modified to account for high damping. A practical approach to consider high damping ratios in design is to build spectra by means of damping correction factors affecting 5% elastic response values. This study proposes damping correction factors (DCFs) expressions for horizontal spectral relative displacement, velocity, and acceleration. The DCFs, derived from European records, are intended for use with seismic codes, in particular Eurocode 8. Consideration of significant duration results in specific expressions for regions of high seismicity, and low-to-moderate seismicity. The new correction factors are compared with those proposed in the literature and the improvements are quantitatively demonstrated.