Browsing by Author "Macedo, Jorge"
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Item A New State-of-the-Art Platform for Probabilistic and Deterministic Seismic Hazard Assessment(2019) Candia, Gabriel; Macedo, Jorge; Jaimes, Miguel A.; Magna-Verdugo, CarolinaA new computational platform for seismic hazard assessment is presented. The platform, named SeismicHazard, allows characterizing the intensity, uncertainty, and likelihood of ground motions from subduction-zone (shallow interface and intraslab) and crustal-zone earthquakes, considering site-specific as well as regional-based assessments. The platform is developed as an object-oriented MATLAB graphical user interface, and it features several state-of-the-art capabilities for probabilistic and deterministic (scenario-based) seismic hazard assessment. The platform integrates the latest developments in performancebased earthquake engineering for seismic hazard assessment, including seismic zonation models, ground-motion models (GMMs), ground-motion correlation structures, and the estimation of design spectra (uniform hazard spectra, classical conditional mean spectrum (CMS) for a unique tectonic setting). In addition to these standard capabilities, the platform supports advanced features, not commonly found in existing seismic hazard codes, such as (a) computation of source parameters from earthquake catalogs, (b) vector-probabilistic seismic hazard assessment, (c) hazard evaluation based on conditional GMMs and user-defined GMMs, (d) uncertainty treatment in the median ground motions through continuous GMM distributions, (e) regional shaking fields, and (f ) estimation of CMS considering multiple GMMs and multiple tectonic settings. The results from the platform have been validated against accepted and well-documented benchmark solutions.Item Correlations of spectral accelerations in the Chilean subduction zone(2020) Candia, Gabriel; Poulos, Alan; Llera, Juan Carlos de la; Crempien, Jorge G.F.; Macedo, JorgeThe correlation between spectral accelerations is key in the construction of conditional mean spectra, the computation of vector-valued seismic hazard, and the assessment of seismic risk of spatially distributed systems, among other applications. Spectral correlations are highly dependent on the earthquake database used, and thus, region-specific correlation models have been developed mainly for earthquakes in western United States, Europe, Middle East, and Japan. Correlation models based on global data sets for crustal and subduction zones have also become available, but there is no consensus about their applicability on a specific region. This study proposes a new correlation model for 5% damped spectral accelerations and peak ground velocity in the Chilean subduction zone. The correlations obtained were generally higher than those observed from shallow crustal earthquakes and subduction zones such as Japan and Taiwan. The study provides two illustrative applications of the correlation model: (1) computation of conditional spectra for a firm soil site located in Santiago, Chile and (2) computation of bivariate hazard for spectral accelerations at two structural periods.Item Ground Motion Correlations from Recorded Mexican Intermediate-depth, Intraslab Earthquakes(2021) Jaimes, Miguel A.; Candia, Gabriel; López-Castañeda, Alhelí; Macedo, JorgePredictive models to estimate correlation coefficients between peak ground acceleration, peak ground velocity, and spectral acceleration residuals for Mexican intermediate-depth, intraslab earthquakes recorded on rock sites are presented in this study. The models were developed for the total, between-events, and within-event residuals using a recent ground-motion prediction equation (GMPE) and an updated ground-motion database. The results support the use of region- and mechanism-specific correlation models for the subduction intraslab zone of Mexico. An example of the application of the proposed correlation coefficient models consisting in evaluating a conditional mean spectrum (CMS), based on the Mexican seismic design normative, is presented.Item New developments for the performance-based assessment of seismically-induced slope displacements(2020-11) Macedo, Jorge; Candia, Gabriel; Lacour, Maxime; Liu, ChenyingThis study presents new developments for the performance-based assessment of seismically-induced slope displacements (D). Performance-based procedures enable a hazard-consistent and rational seismic design of slope systems; hence, their use in practice is appealing. However, they are not the standard in engineering practice because their use is considered too complex to be used for non-critical projects. The developments presented in this study allow the straightforward estimation of displacement hazard curves (DHC) for a wide range of slope systems subjected to earthquakes in different tectonic settings (i.e., shallow crustal, and subduction), considering a rigorous quantification of the existing uncertainties. The new developments include 1) full integration of probabilistic seismic hazard assessments (PSHA), and the estimation of DHCs, 2) automatic estimation of DHC for D models with multiple intensity measures through vector PSHA, 3) estimation of DHC for systems with contributions from multiple tectonic settings, 4) uncertainty treatment (i.e., epistemic and aleatory) on DHCs, through a logic tree scheme, 5) deaggregation of earthquake scenarios from DHCs, and 6) uncertainty quantification on DHCs through the polynomial chaos theory. The new developments are implemented in a MATLAB graphical user interface (GUI) to facilitate its use by engineers and researchers. We discuss illustrative examples and guidelines for the application of the GUI to evaluate the seismic performance of different slope systems that are affected by earthquakes from multiple tectonic settings.Item Performance-based analysis of Transit tunnels in the Chilean subduction zone(2022) Lyon, Benjamín; Candia, Gabriel; Gutiérrez, Carlos; Macedo, JorgeIn this article, we study the seismic response of a shallow metro tunnel in a subduction zone environment and the use of a performance-based approach to develop seismic demand hazard curves (SDHC) of key engineering demand parameters, such as drift ratio, surface settlement, bending moment, and axial loads. The tunnel consists of a 6-m diameter sprayed concrete lining in medium dense soil and is located in Santiago, Chile. To simulate its seismic response, a finite element model of the soil–tunnel system was implemented in OpenSees and validated against centrifuge test results, linear-equivalent solutions for a 1D soil column, and single elements in cyclic simple shear. The tunnel response was computed for 112 ground motions, selected and scaled using the conditional scenario approach. This approach assigns a rate of occurrence to each ground motion and therefore, allows for a direct computation of annual exceedance rates of the tunnel response parameters. For instance, at this specific location, the 2500-yr return period drift ratio in the lining is approximately 0.25% as a result of large deformations imposed by the surrounding soil. Likewise, axial loads between 0.3 and 1.0 MN/m and vending moments of ±0.2 MN∙m/m are apparent from the axial load-moment interaction diagrams; these results are of great value for the design and verification of the tunnel based on the collapse or life-safety limit states. Notably, the current formulation relaxes the assumption of scaling ground motions to a particular intensity measure and can be a computationally efficient alternative to standard incremental dynamic analysesItem Performance-based assessment of the seismic pseudo-static coefficient used in slope stability analysis(2020) Macedo, Jorge; Candia, GabrielPseudo-static slope stability procedures are often employed to evaluate the seismic performance of geotechnical slope systems, at least in the initial evaluation stages. To yield meaningful results, these methods should rely on parameters that are representative of the existing seismic demand and the properties of the geotechnical slope system being evaluated. This study proposes a performance-based probabilistic procedure to estimate the seismic pseudo-static coefficient (SPC) in a rational and transparent manner. The proposed procedure has its cornerstone on the evaluation of seismically-induced displacement (D) hazard curves, and it provides SPC estimations that are consistent with the allowable D level that a geotechnical structure can sustain, the properties of the sliding mass, and the seismic demand at the slope site. In addition, the calculated SPC can be directly associated with a return period or hazard design level for D. The proposed procedure can be applied to evaluate the seismic performance of a wide range of geotechnical slope systems potentially affected by earthquakes from different tectonic settings, such as subduction and shallow crustal earthquake zones (or a combination of both). The proposed procedure is implemented in a computational platform that facilitates its straightforward use in engineering practice. The implementations are fully automated for South America (i.e., Peru, Chile, Ecuador), Mexico, and the United States, but the proposed framework can be applied worldwide. Finally, an illustrative example for the application of the procedure in the seismic stability assessment of a slope system is provided.Item Performance-based probabilistic assessment of liquefaction-induced building settlements(2021) Liu, Chenying; Macedo, Jorge; Candia, GabrielThe current state of practice in the estimation of liquefaction-induced building settlements (LIBS) relies on pseudoprobabilistic approaches in which the estimation of ground motion intensity measures (IMs) is separated from the estimation of LIBS. In contrast, in a performance-based probabilistic approach, the estimation of the IM hazard is coupled with the estimation of the LIBS hazard. Thus, engineers can obtain LIBS estimates that are directly related to a selected design hazard level (or return period), which is more consistent with performance-based design. In this study, we present new developments for the performance-based probabilistic evaluation of LIBS, including 1) the performance-based assessment of LIBS considering the hazard from a single IM in the context of scalar probabilistic seismic hazard assessment (PSHA), 2) the performance-based assessment of LIBS considering the hazard from multiple IMs in the context of vector PSHA, 3) deaggregation of earthquake scenarios from LIBS hazard curves, 4) estimation of LIBS hazard curves in areas where earthquakes from multiple tectonic settings can occur (e.g., shallow crustal, subduction), and 5) treatment of uncertainties (i.e., aleatory and epistemic). The developments are implemented in a computational platform named "LIBS", which is fully coupled with PSHA assessments and facilitates the straightforward performance-based estimation of LIBS in engineering practice. Finally, we perform comparisons of performance-based and pseudoprobabilistic-based estimates of LIBS and share insights from the comparisons.