Hybrid Low-Viscous-Damping Inelastic Displacement Ratios for Seismic Design and Assessment of Structures

ABSTRACT

Until recently, the viscous damping ratio pervasively assumed has been $\zeta =5\mathrm{\%}$. However, the dynamic identification of the experimental response recorded in recent large-scale shake-table tests shows that lower levels of viscous damping are more appropriate when material nonlinearities are explicitly accounted for. This paper investigates a hybrid constant-ductility inelastic displacement ratio, $C_{\mu 2}$, which identifies the inelastic demand for a viscous damping ratio $\zeta =2\mathrm{\%}$ when the elastic demand for $\zeta =5\mathrm{\%}$ is known. A comprehensive statistical analysis is developed, and analytical estimates are provided, for inelastic single-degree-of-freedom systems with a wide variation of the constitutive parameters and a large earthquake database.

KEYWORDS:

• 2% viscous damping
• inelastic spectra
• displacement-based design
• self-centering systems
• performance-based seismic design
• nonlinear time history analysis

Acknowledgments

The author wishes to acknowledge Prof. J. Restrepo, University of California San Diego, for the contribution offered at the early stage of this research. For the support in the analysis process and the several comments provided, the author also wishes to acknowledge Prof. A. Carr and Prof. T. J. Sullivan, University of Canterbury, New Zealand. This study has benefitted from an important review process, and the anonymous reviewers are sincerely acknowledged for their valuable time and precious contribution.

Additional information

Funding

This project was partially supported by QuakeCoRE, a New Zealand Tertiary Education Commission-funded Centre. This is QuakeCoRE publication number 0610.