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Earthquakes and Structures Volume 13, Number 1, July 2017 , pages 59-66 DOI: https://doi.org/10.12989/eas.2017.13.1.059 |
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Seismic structural demands and inelastic deformation ratios: Sensitivity analysis and simplified models |
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Benazouz Chikh, Nacer Laouami, Ahmed Mebarki, Moussa Leblouba, Youcef Mehani, Abderrahmane Kibboua, Mohamed Hadid and Djillali Benouar
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| Abstract | ||
| Modern seismic codes rely on performance-based seismic design methodology which requires that the structures withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation (ratio between the inelastic and elastic maximum lateral displacement demands) for various inelastic spectra. This paper investigates the inelastic response spectra through the ductility demand µ, the yield strength reduction factor Ry, and the inelastic deformation ratio. They depend on the vibration period T, the post-to-preyield stiffness ratio α, the peak ground acceleration (PGA), and the normalized yield strength coefficient η (ratio of yield strength coefficient divided by the PGA). A new inelastic deformation ratio Cη is defined; it is related to the capacity curve (pushover curve) through the coefficient (η) and the ratio (α) that are used as control parameters. A set of 140 real ground motions is selected. The structures are bilinear inelastic single degree of freedom systems (SDOF). The sensitivity of the resulting inelastic deformation ratio mean values is discussed for different levels of normalized yield strength coefficient. The influence of vibration period T, post-to-preyield stiffness ratio α, normalized yield strength coefficient η, earthquake magnitude, ruptures distance (i.e., to fault rupture) and site conditions is also investigated. A regression analysis leads to simplified expressions of this inelastic deformation ratio. These simplified equations estimate the inelastic deformation ratio for structures, which is a key parameter for design or evaluation. The results show that, for a given level of normalized yield strength coefficient, these inelastic displacement ratios become non sensitive to none of the rupture distance, the earthquake magnitude or the site class. Furthermore, they show that the post-to-preyield stiffness has a negligible effect on the inelastic deformation ratio if the normalized yield strength coefficient is greater than unity. | ||
| Key Words | ||
| deformation ratio; yield strength reduction factor; ductility; inelastic spectra; earthquakes; seismic response | ||
| Address | ||
| Benazouz Chikh, Nacer Laouami, Youcef Mehani, Abderrahmane Kibboua: National Earthquake Engineering Research Center, CGS, Rue Kaddour Rahim, BP 252 Hussein-Dey, Algiers, Algeria Ahmed Mebarki: University Paris-Est, Laboratoire Modelisation et Simulation Multi Echelle (MSME), UMR 8208 CNRS, 5 Bd Descartes, 77454 Marne-La-Vallee, France Moussa Leblouba: Department of Civil & Environmental Engineering, College of Engineering, University of Sharjah, P.O. Box 27272 Sharjah, United Arab Emirates Mohamed Hadid: National School of Built and Ground Works Engineering (ENSTP), 01 Rue SidiGaridi, Vieux Kouba 16003, Algiers, Algeria Djillali Benouar: University of Science & Technology HouariBoumediene (USTHB), Faculty of Civil Engineering, BP 32, 16111 El-Alia / Bab Ezzouar, Algiers, Algeria | ||