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Seismic response of high plasticity clays during extreme events
Abstract Mexico City high plasticity clays exhibit a small degree of nonlinearity for shear strains as large as 0.1%, which leads to both moderate shear stiffness degradation and small to medium damping increment, even for long duration subduction strong ground motions, such as the 8.1M w 1985Michoacan earthquake. Nonetheless, current seismic design criteria of strategic infrastructure used worldwide have striven for having larger return periods for establishing the seismic environment, considering recent large magnitude (M>8.5M w) events. This paper presents the study of the seismic response of typical high plasticity clays found in the so-called Texcoco Lake, in the surrounding of Mexico City valley, for larger to extreme earthquakes. The shear wave velocity profile was characterized using a down-hole test. The seismic environment was established from a set of uniform hazard response spectra developed for a nearby rock outcrop for return periods of 125, 250, 475 and 2475 years. A time-domain spectral matching was used to develop acceleration time histories compatible with each uniform hazard response spectrum. Both frequency and time domain site response analyses were carried out considering each seismic scenario. Ground nonlinearities were clearly observed in the soil response during extreme ground shaken, which increases rapidly with the return period. This fact must be taken into account to avoid costly and potentially unsafe seismic designs.
Graphical abstract Computed response spectra for each return period for site 2 considering (a) equivalent linear properties and (b) non-linear hysteretic model. Display Omitted
Highlights High plasticity clays under extreme shaking exhibit significant nonlinearities. Nonlinearities were mostly due to hysteretic damping. The amplification factor decreases when the return period increases. Nonlinearities must be taken into account to avoid costly seismic designs.
Seismic response of high plasticity clays during extreme events
Abstract Mexico City high plasticity clays exhibit a small degree of nonlinearity for shear strains as large as 0.1%, which leads to both moderate shear stiffness degradation and small to medium damping increment, even for long duration subduction strong ground motions, such as the 8.1M w 1985Michoacan earthquake. Nonetheless, current seismic design criteria of strategic infrastructure used worldwide have striven for having larger return periods for establishing the seismic environment, considering recent large magnitude (M>8.5M w) events. This paper presents the study of the seismic response of typical high plasticity clays found in the so-called Texcoco Lake, in the surrounding of Mexico City valley, for larger to extreme earthquakes. The shear wave velocity profile was characterized using a down-hole test. The seismic environment was established from a set of uniform hazard response spectra developed for a nearby rock outcrop for return periods of 125, 250, 475 and 2475 years. A time-domain spectral matching was used to develop acceleration time histories compatible with each uniform hazard response spectrum. Both frequency and time domain site response analyses were carried out considering each seismic scenario. Ground nonlinearities were clearly observed in the soil response during extreme ground shaken, which increases rapidly with the return period. This fact must be taken into account to avoid costly and potentially unsafe seismic designs.
Graphical abstract Computed response spectra for each return period for site 2 considering (a) equivalent linear properties and (b) non-linear hysteretic model. Display Omitted
Highlights High plasticity clays under extreme shaking exhibit significant nonlinearities. Nonlinearities were mostly due to hysteretic damping. The amplification factor decreases when the return period increases. Nonlinearities must be taken into account to avoid costly seismic designs.
Seismic response of high plasticity clays during extreme events
Mayoral, Juan M. (author) / Castañon, Ernesto (author) / Sarmiento, Neftalí (author)
Soil Dynamics and Earthquake Engineering ; 77 ; 203-207
2015-05-22
5 pages
Article (Journal)
Electronic Resource
English
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