ANID

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Browsing ANID by browse.metadata.categoria "Ciencias de la tierra"

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    Full-scale shaking table test and numerical modeling of a 3000-liter legged storage tank isolated with a vertical rocking isolation system
    (WILEY, 2022) Reyes, Sergio, I; Almazán Campillay, José Luis; Vassiliou, Michalis F.; Tapia Flores, Nicolás Felipe; Colombo, Jose, I; Llera Martin, Juan Carlos de la
    This paper presents the numerical and experimental evaluation of a vertical-rocking isolation (VRI). This evaluation is done by 1-D shaking table tests performed on a full-scale legged storage tank of 3000-liters capacity and its representation through a simple yet representative rigid lumped-mass model approach. The isolation system setup consisted of four ISO3D-2G devices, each one placed on each leg of the tank, which uses high-damping natural rubber to generate the restoring and dissipative forces. The ISO3D-2G device is vertically flexible and laterally rigid, enabling the isolation mechanism of the rocking motion of the tank. The experiments were carried out using three white noise for the system identification and 17 ground motions inputs for the system validation. The measured variables included the lateral acceleration and displacement of the tank, and the vertical and rotational behavior of the isolation interface. The identification results showed a vertical-rotational coupled fundamental mode that is highly dependent on the amplitude of deformation, with a period varying from 0.5 to more than 1 s, depending on the intensity of the motion. The maximum displacement of the tank at the top remained below 13 cm with total accelerations of nearly 0.3 g, both for motions with Peak Ground Acceleration (PGA) values ranging from 0.3 to 0.8 g. The mean maximum values were predicted with the simplified model with errors of less than 10% and 21% for displacements and accelerations, respectively. Finally, the results show that the behavior of vertical-rocking isolated structures can be predicted by simplified models with reasonable errors and that the development of simple design guidelines and equations for VRI systems is possible.
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    Rupture parameter sensitivity of low frequency ground motion response spectra using synthetic scenarios in North Chile
    (SPRINGER, 2021) Fortuño Jara, Catalina Pía; Llera Martin, Juan Carlos de la; Gonzalez, Gabriel; Gonzalez, Juan; Aguirre Aparicio, Paula
    This research performs a sensitivity analysis of response spectrum values for various physical earthquake parameters, which are used to generate synthetic seismograms consistent with the expected seismicity in north Chile. Sensitivity analyses are based on the earthquake scenario and slip distribution model of the 2014, M-w 8.1 Pisagua earthquake, and seven other physically plausible interplate events for north Chile. A finite-fault rupture model, and slip distribution of the Pisagua earthquake, were obtained using inversion of InSAR and GPS data. Three other rupture models based on previous studies of interplate locking for north Chile and capable of generating M-w 8.3-8.6 earthquakes with an estimated maximum slip of 9.2 m, were incorporated in the analyses. Also, four additional scenarios with moment magnitudes in the range M-w 8.6-8.9 were generated by concatenating these physical scenarios into larger rupture areas within the north segment. Using these scenarios, synthetic ground motions were built at four observation sites: Pisagua, Iquique, Tocopilla, and Calama. Response sensitivity was studied for three key rupture parameters: mean rupture velocity, slip rise-time, and rupture directivity. Responses selected were peak ground displacement (PGD), spectral pseudo-velocities, S-v, and spectral displacements, S-d. First and second order variations of PGD, S-v, and S-d relative to the source parameters were computed and used together with a Taylor series expansion to propagate uncertainty into the responses as a function of v(r) and rise-time t(r). To study the effect of rupture directivity, three different foci locations were considered for each scenario: north, south, and at the centroid of the slip model. Response PGD values show no clear trends with rupture velocity, v(r); however, the variability increases as the system period increases. The effect of the slip rise-time is significant, and as t(r) increases, the spectral responses tend to decrease, suggesting that shorter slip rise-times lead to higher seismic demands in long period structures. The results obtained for the directivity analysis suggest that two factors control the expected waveforms and spectral responses: first, the direction of the rupture relative to the location of each site, and the hypocentral distance.