Browsing by Author "Miranda, Eduardo"

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    A simplified and versatile element model for elastomeric seismic isolation bearings
    (SAGE PUBLICATIONS INC, 2021) Miranda Camus, Sebastián; Miranda, Eduardo; Llera Martin, Juan Carlos de la
    A novel approach for two-dimensional modeling of elastomeric bearings using three springs in parallel is presented. This simplified element model considers as follows: (1) an elastoplastic spring with a smooth transition between branches; (2) a linear elastic spring; and (3) a non-linear elastic spring, and is fully defined by only six parameters. The main advantages of the simplified model are twofold: (1) versatility, as a single model is capable of accurately reproducing the main characteristics of the hysteretic behavior of different types of rubber-based seismic isolators, including low damping rubber bearings (LDRBs), high damping rubber bearings (HDRBs), and lead-core rubber bearings (LRBs) and (2) simplicity, as it requires fewer parameters and it is easier to calibrate from experimental cyclic test results than most currently available models. Model parameters' identification is illustrated using quasi-static cyclic and earthquake simulator tests of HDRBs and LRBs, demonstrating that the model shows a good agreement between the test-measured and model-predicted hysteretic behavior. Different objective functions are evaluated in the optimization procedure, and their effect on the identified parameters is studied and discussed. This practitioner-oriented model is particularly amenable for implementation in general-purpose structural analysis software. Its usage is strongly recommended as an initial-stage design tool to select the optimal isolation system for a specific project.
  • Thumbnail Image
    Item
    Development and Testing of a Friction/Sliding Connection to Improve the Seismic Performance of Gypsum Partition Walls
    (2019) Araya Letelier, Gerardo Andrés; Miranda, Eduardo; Deierlein, Gregory G.
  • Thumbnail Image
    Item
    Performance of port facilities in southern Chile during the 27 february 2010 Maule Earthquake
    (SAGE PUBLICATIONS INC, 2012) Brunet Gutiérrez, Santiago José; Llera Martin, Juan Carlos de la; Jacobsen Pohlenz, Andrés; Miranda, Eduardo; Meza, Cristian
    This article describes the seismic performance of a group of ports in southern Chile during the 27 February 2010 Maule, Chile, earthquake. Direct costs in damage for these ports have been estimated in slightly less than US$300 million. Similarly to the performance of other ports in previous earthquakes, the most common failures observed were soil related, and include soil liquefaction, lateral spreading, and pile failures. Structural failures were mostly due to short pile effects and natural torsion. This situation is contrasted herein with the performance of the South Coronel Pier, which was seismically isolated in 2007. The isolated portion of this port remained operational after the earthquake, which was the main design goal. Post-earthquake preliminary analyses indicate that the structure was subjected to deformations and forces of approximately 60% to 70% of their design values, respectively. Piles and superstructure remained within elastic range, while the isolators experienced important nonlinear deformations. [DOI: 10.1193/1.4000022]
  • No Thumbnail Available
    Item
    Seasonal variation in the range areas of the diurnal rodent Octodon degus
    (2010) Quirici, Veronica; Castro, Rodrigo A.; Ortiz-Tolhuysen, Liliana; Chesh, Adrian S.; Burger, Joseph Robert; Miranda, Eduardo; Cortes, Arturo; Hayes, Loren D.; Ebensperger, Luis A.
    Both breeding activity and abundance and quality of available food are expected to influence daily movements of animals. Animals are predicted to range over large areas to meet high energy demands associated with reproduction (females) or to Increase mating success (males). However. animals should expand their range areas whenever food conditions deteriorate. To examine the extent to which breeding activity versus food availability influence space use, we compared the size and location of range areas (home ranges) of the degu (Octodon degus), a diurnal rodent from semiarid environments of north-central Chile. during the austral winter and summer seasons. Degus produce young during the austral spring (September-October) when high-quality food is readily available In contrast, degus do not breed during the austral summer (January-March) when food is scarce and of low quality. We predicted that degus would range over smaller areas in winter if the availability of food has a greater influence on space than breeding activity. Individuals were radiotracked in winter and the following summer over a 3-year period. Surveys of herbaceous cover were conducted during winter and summer to determine seasonal changes in the abundance and quality of primary food In summer degus expanded and moved the location of their range areas to locations with available food Given that preferred food was less abundant in summer than winter, we suggest that degu range areas are strongly influenced by food conditions DOI 10 1644/08-MAMM-A-337.1
  • No Thumbnail Available
    Item
    The effect of spectral shape on damping modification factors
    (2020) Miranda Camus, Sebastián; Miranda, Eduardo; Llera Martin, Juan Carlos de la
    The main objective of this study is to investigate the effect of spectral shape on damping modification factors η used in equivalent static and response spectrum analyses of structures with damping ratios that are different from 5% critical damping. Record-to-record variability of η is also evaluated through a statistical analysis of 5270 ground motions records from 1137 interface earthquakes recorded in Chile. The effect of spectral shape is studied using recently developed spectral shape metrics SaRatio and epsilon (ε) and evaluating their use as possible predictors for η. Similarly to previous investigations, this article also examines the effect of oscillator period, earthquake magnitude, and earthquake duration for different levels of damping ratio. Results suggest that SaRatio is an effective predictor of η, particularly for highly damped structures. However, results also indicate that for rock and firm sites, earthquake faulting mechanism and site class do not have a significant influence on η. A simple period-independent regression model for η as a function of SaRatio and damping ratio is proposed. A comparison between median η from this study and those in current Chilean seismic codes shows that code factors are unconservative.
  • No Thumbnail Available
    Item
    Uncertainty on measurement of elastomeric isolators effective properties
    (2021) Miranda Camus, Sebastián; Llera Martin, Juan Carlos de la; Miranda, Eduardo
    Elastomeric isolators are subjected to a series of non-destructive tests with several repeated deformation cycles. For each cycle, effective properties are calculated and afterward averaged. Despite their variability, and therefore their inherent uncertainties, these properties are treated as deterministic values by seismic design procedures. In this research, these uncertainties are quantified, based on the Guide to the expression of Uncertainty in Measurement, GUM, and Monte-Carlo simulations, considering variability between repetitions and instrumentation errors. Uncertainties were calculated for a dataset of 2,498 isolators' test results, finding that the maximum relative expanded uncertainty was 12%. The GUM and Monte-Carlo methods lead to similar results, and higher-order effects in the GUM assessment were negligible. A comprehensive analysis to evaluate the influence of the directly-measured quantities in the properties uncertainties was performed. Results showed that forces and displacements measurement errors are equally relevant in stiffness uncertainties, but force measurement errors primarily control damping uncertainties.