Inelastic spectra to predict period elongation of structures under earthquake loading

Evangelos Katsanos, A.G. Sextos

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Period lengthening, exhibited by structures when subjected to strong ground motions, constitutes an implicit proxy of structural inelasticity and associated damage. However, the reliable prediction of the inelastic period is tedious and a multi-parametric task, which is related to both epistemic and aleatory uncertainty. Along these lines, the objective of this paper is to investigate and quantify the elongated fundamental period of reinforced concrete structures using inelastic response spectra defined on the basis of the period shift ratio (Tin/Tel). Nonlinear oscillators of varying yield strength (expressed by the force reduction factor, Ry), post-yield stiffness (ay) and hysteretic laws are examined for a large number of strong motions. Constant-strength, inelastic spectra in terms of Tin/Tel are calculated to assess the extent of period elongation for various levels of structural inelasticity. Moreover, the influence that structural characteristics (Ry, ay and degrading level) and strong-motion parameters (epicentral distance, frequency content and duration) exert on period lengthening are studied. Determined by regression analyses of the data obtained, simplified equations are proposed for period lengthening as a function of Ry and Tel. These equations may be used in the framework of the earthquake record selection and scaling.
    Original languageEnglish
    JournalEarthquake Engineering and Structural Dynamics
    Pages (from-to)1765-1782
    ISSN0098-8847
    DOIs
    Publication statusPublished - 2015

    Keywords

    • Period elongation
    • Inelastic spectra
    • Nonlinear response history analyses
    • Earthquake strong ground motions
    • Force reduction factor

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