Seismic fragility of RC structures under mainshockaftershock sequences recorded on soft soil conditions

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    Abstract

    Past earthquake episodes of moderate-to-high magnitude have shown that strong mainshock trigger usually strong aftershocks forming, in such a way, the so-called mainshock-aftershock (MSAS) sequences. The latter can normally induce higher seismic losses to structures and infrastructures compared to the single mainshock event. High vulnerability has been also detected for structural systems being subjected to the soft soil earthquake strong ground motions due to the soft soils-driven amplification in structural demand. Along these lines, this study investigates the seismic fragility of an existing reinforced concrete (rc) structure subjected to MSAS sequences recorded on soft soil profiles. To this end, a preliminary selection of 28 and 52 soft-soil mainshocks and aftershocks strong GMs respectively served the basis to generate 36 artificial earthquake sequences. The latter were made of six mainshocks and six aftershocks seismic motions that are representative of the initially formed sets of records in terms of the predominant period, Tg, and the strong ground motion duration. An existing seven-story rc building located in Van Nuys, California, was modelled by using the OpenSees finite element code. The measured response of the building during the Northridge (1994) earthquake episode was used to validate the finite element model developed herein. Nonlinear time history analysis was performed and the soft-soil MSAS-induced structural response (i.e., roof drift, maximum interstory drift ratio and maximum residual interstory drift ratio) was comparatively assessed with the response induced by MSAS sequences recorded on firm soil conditions. Fragility analysis was also conducted and the relevant fragility curves were estimated accounting for varying intensity of the aftershocks. Based on the results derived herein, the firm-soil MSAS led to higher structural collapse capacity compared to the one that was calculated by using the soft-soil MSAS, the latter being more profound when the building was subjected to aftershocks with increased intensity.
    Original languageEnglish
    Title of host publicationProceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering
    Volume2
    PublisherNational Technical University of Athens
    Publication date2019
    Pages2649-2660
    ISBN (Electronic)9786188284470
    Publication statusPublished - 2019
    Event7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering - Crete, Greece
    Duration: 24 Jun 201926 Jun 2019
    Conference number: 7

    Conference

    Conference7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering
    Number7
    Country/TerritoryGreece
    CityCrete
    Period24/06/201926/06/2019
    SeriesCompdyn Proceedings
    ISSN2623-3347

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