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Bayesian approach for probabilistic site characterization using cone penetration tests / Zijun Cao in Journal of geotechnical and geoenvironmental engineering, Vol. 139 N° 2 (Février 2013) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 2 (Février 2013) . - pp. 267-276 Titre : Bayesian approach for probabilistic site characterization using cone penetration tests Type de document : texte imprimé Auteurs : Zijun Cao, Auteur ; Yu Wang, Auteur Année de publication : 2013 Article en page(s) : pp. 267-276 Note générale : geotechnique Langues : Anglais (eng) Mots-clés : Bayesian  system  identification;  Bayesian  model  class  selection;  prior  knowledge;  spatial  variability;  statistically  homogenous  layer;  random  field Résumé : This paper develops a Bayesian approach for probabilistic site characterization (i.e., on both stratigraphy and soil properties) using cone penetration tests (CPTs). The available site information prior to the project (e.g., existing geological maps, geotechnical reports, and local experience) is used in the Bayesian approach as prior knowledge, and it is integrated systematically with results of CPTs that are performed deliberately for the project. The inherent spatial variability of soil is modeled explicitly by random field theory. The proposed approach contains two major components: a Bayesian model class selection method to identify the most probable number of statistically homogenous layers of soil and a Bayesian system identification method to estimate the most probable layer thicknesses and soil properties probabilistically. Equations are derived for the Bayesian approach, and the proposed approach is illustrated using a set of real CPT data obtained from a site in Netherlands. It has been shown that the proposed approach correctly identifies the number and thicknesses/boundaries of the statistically homogenous layers of soil and provides proper probabilistic characterization of soil properties. The Bayesian approach provides a means to identify the statistically homogenous layers progressively by gradually zooming into local differences with improved resolution, and it also contains a mechanism to determine when to stop such zooming. In addition, a sensitivity study is performed to explore the effect of prior knowledge. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000765 [article] Bayesian approach for probabilistic site characterization using cone penetration tests [texte imprimé] / Zijun Cao, Auteur ; Yu Wang, Auteur . - 2013 . - pp. 267-276. geotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 139 N° 2 (Février 2013) . - pp. 267-276 Mots-clés : Bayesian  system  identification;  Bayesian  model  class  selection;  prior  knowledge;  spatial  variability;  statistically  homogenous  layer;  random  field Résumé : This paper develops a Bayesian approach for probabilistic site characterization (i.e., on both stratigraphy and soil properties) using cone penetration tests (CPTs). The available site information prior to the project (e.g., existing geological maps, geotechnical reports, and local experience) is used in the Bayesian approach as prior knowledge, and it is integrated systematically with results of CPTs that are performed deliberately for the project. The inherent spatial variability of soil is modeled explicitly by random field theory. The proposed approach contains two major components: a Bayesian model class selection method to identify the most probable number of statistically homogenous layers of soil and a Bayesian system identification method to estimate the most probable layer thicknesses and soil properties probabilistically. Equations are derived for the Bayesian approach, and the proposed approach is illustrated using a set of real CPT data obtained from a site in Netherlands. It has been shown that the proposed approach correctly identifies the number and thicknesses/boundaries of the statistically homogenous layers of soil and provides proper probabilistic characterization of soil properties. The Bayesian approach provides a means to identify the statistically homogenous layers progressively by gradually zooming into local differences with improved resolution, and it also contains a mechanism to determine when to stop such zooming. In addition, a sensitivity study is performed to explore the effect of prior knowledge. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000765

Economic design optimization of foundations / Yu Wang in Journal of geotechnical and geoenvironmental engineering, Vol. 134 n°8 (Août 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°8 (Août 2008) . - pp. 1097–1105 Titre : Economic design optimization of foundations Type de document : texte imprimé Auteurs : Yu Wang, Auteur ; Fred H. Kulhawy, Auteur Année de publication : 2008 Article en page(s) : pp. 1097–1105 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Economic  factors  Cost  estimates  Optimization  Spread  foundations  Limit  states  Serviceability Résumé : A geotechnical foundation design should address at least three basic requirements: ultimate limit state (ULS), serviceability limit state (SLS), and economics. Most conventional design approaches focus on ULS and/or SLS optimization, with economics being evaluated afterwards. As an alternative, this paper develops a design approach that explicitly considers the construction economics and results in a foundation that has the minimum construction cost. This design approach is expressed as an optimization process, in which the objective is to minimize construction cost, with the design parameters and design requirements as the optimization variables and constraints, respectively. This design approach is illustrated using a spread footing example. Because construction costs vary by locale, the economically optimized designs differ regionally. Sensitivity studies on soil properties and design requirements show that, for typical spread footing designs in cohesionless soils, Young’s modulus (E) and the effective friction angle (ϕ′) are the key parameters. A quantitative assessment illustrates the importance of soil property variability on cost. It is also found that, for typical spread footing designs, a relatively stringent ULS requirement generally ensures fulfillment of the SLS requirement. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A8%2810 [...] [article] Economic design optimization of foundations [texte imprimé] / Yu Wang, Auteur ; Fred H. Kulhawy, Auteur . - 2008 . - pp. 1097–1105. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 n°8 (Août 2008) . - pp. 1097–1105 Mots-clés : Economic  factors  Cost  estimates  Optimization  Spread  foundations  Limit  states  Serviceability Résumé : A geotechnical foundation design should address at least three basic requirements: ultimate limit state (ULS), serviceability limit state (SLS), and economics. Most conventional design approaches focus on ULS and/or SLS optimization, with economics being evaluated afterwards. As an alternative, this paper develops a design approach that explicitly considers the construction economics and results in a foundation that has the minimum construction cost. This design approach is expressed as an optimization process, in which the objective is to minimize construction cost, with the design parameters and design requirements as the optimization variables and constraints, respectively. This design approach is illustrated using a spread footing example. Because construction costs vary by locale, the economically optimized designs differ regionally. Sensitivity studies on soil properties and design requirements show that, for typical spread footing designs in cohesionless soils, Young’s modulus (E) and the effective friction angle (ϕ′) are the key parameters. A quantitative assessment illustrates the importance of soil property variability on cost. It is also found that, for typical spread footing designs, a relatively stringent ULS requirement generally ensures fulfillment of the SLS requirement. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A8%2810 [...]

Expanded reliability-based design approach for drilled shafts / Yu Wang in Journal of geotechnical and geoenvironmental engineering, Vol. 137 N° 2 (Fevrier 2011) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 2 (Fevrier 2011) . - pp. 140-149 Titre : Expanded reliability-based design approach for drilled shafts Type de document : texte imprimé Auteurs : Yu Wang, Auteur ; Siu-Kui Au, Auteur ; Fred H. Kulhawy, Auteur Année de publication : 2011 Article en page(s) : pp. 140-149 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Uncertainty  Foundation  Pile  Limit  states  Simulations Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : This paper develops a more general reliability-based design approach for drilled shafts that formulates the design process as an expanded reliability problem in which Monte Carlo simulations (MCS) are used in the design. Basic design parameters, such as the shaft diameter (B) and depth (D), are formulated as discrete uniform random variables. Then the design process becomes one in which failure probabilities are developed for various combinations of B and D [i.e., conditional probability p(Failure∣B,D)] and are compared with a target probability of failure pT. Equations are derived for this expanded reliability-based design (RBDE) approach, and criteria are established for the minimum number of MCS samples to ensure a desired level of accuracy. Its usefulness is illustrated using a drilled shaft design example. This RBDE approach has the following advantages: (1) it gives results that agree well with current RBD designs, but it improves the resolutions of the designs; (2) it offers design engineers insight into how the expected design performance level changes as B and D change; (3) it gives design engineers the ability to adjust pT, without additional calculation effort, to accommodate specific needs of a particular project; and (4) it is transparent and “visible” to design engineers who are given the flexibility to include uncertainties deemed appropriate. Finally, the effects of uncertainties in the at-rest horizontal soil stress coefficient (K0) and allowable displacement (ya) are illustrated using this approach. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i2/p140_s1?isAuthorized=no [article] Expanded reliability-based design approach for drilled shafts [texte imprimé] / Yu Wang, Auteur ; Siu-Kui Au, Auteur ; Fred H. Kulhawy, Auteur . - 2011 . - pp. 140-149. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 137 N° 2 (Fevrier 2011) . - pp. 140-149 Mots-clés : Uncertainty  Foundation  Pile  Limit  states  Simulations Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : This paper develops a more general reliability-based design approach for drilled shafts that formulates the design process as an expanded reliability problem in which Monte Carlo simulations (MCS) are used in the design. Basic design parameters, such as the shaft diameter (B) and depth (D), are formulated as discrete uniform random variables. Then the design process becomes one in which failure probabilities are developed for various combinations of B and D [i.e., conditional probability p(Failure∣B,D)] and are compared with a target probability of failure pT. Equations are derived for this expanded reliability-based design (RBDE) approach, and criteria are established for the minimum number of MCS samples to ensure a desired level of accuracy. Its usefulness is illustrated using a drilled shaft design example. This RBDE approach has the following advantages: (1) it gives results that agree well with current RBD designs, but it improves the resolutions of the designs; (2) it offers design engineers insight into how the expected design performance level changes as B and D change; (3) it gives design engineers the ability to adjust pT, without additional calculation effort, to accommodate specific needs of a particular project; and (4) it is transparent and “visible” to design engineers who are given the flexibility to include uncertainties deemed appropriate. Finally, the effects of uncertainties in the at-rest horizontal soil stress coefficient (K0) and allowable displacement (ya) are illustrated using this approach. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v137/i2/p140_s1?isAuthorized=no

Measurement of ass transfer rates in adsorbents / Timothy J. Giesy in Industrial & engineering chemistry research, Vol. 51 N° 35 (Septembre 2012) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 51 N° 35 (Septembre 2012) . - pp. 11509–11517 Titre : Measurement of ass transfer rates in adsorbents : New combined - technique frequency response apparatus and application to CO2 in 13X zeolite Type de document : texte imprimé Auteurs : Timothy J. Giesy, Auteur ; Yu Wang, Auteur ; M. Douglas LeVan, Auteur Année de publication : 2012 Article en page(s) : pp. 11509–11517 Note générale : Industrial chemistry Langues : Anglais (eng) Mots-clés : Mass  transfer  Adsorbents Résumé : A new combined-technique frequency response apparatus has been developed for studying mass transfer in porous adsorbents. This new apparatus can perform pressure-swing, volume-swing, and concentration-swing frequency response experiments, enabling it to investigate mass transfer of pure components and binary gas mixtures in adsorbents over a wide frequency range. To demonstrate the capabilities of the apparatus, pressure-swing and volume-swing frequency response experiments were performed in tandem to study transport of pure CO2 in 13X zeolite beads over the frequency range from 10–4 Hz to 10 Hz at pressures from 0.125 to 1 bar. Frequency response spectra show that transport in this system is governed by a nonisothermal macropore diffusion resistance with diffusion occurring by a Knudsen-type mechanism. Macropore diffusion control is confirmed by the existence of particle size dependence of the system’s dynamic response. In smaller zeolite particles, the macropore diffusion resistance is lower, and macropore diffusion becomes less important to the system response. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3014204 [article] Measurement of ass transfer rates in adsorbents : New combined - technique frequency response apparatus and application to CO2 in 13X zeolite [texte imprimé] / Timothy J. Giesy, Auteur ; Yu Wang, Auteur ; M. Douglas LeVan, Auteur . - 2012 . - pp. 11509–11517. Industrial chemistry Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 51 N° 35 (Septembre 2012) . - pp. 11509–11517 Mots-clés : Mass  transfer  Adsorbents Résumé : A new combined-technique frequency response apparatus has been developed for studying mass transfer in porous adsorbents. This new apparatus can perform pressure-swing, volume-swing, and concentration-swing frequency response experiments, enabling it to investigate mass transfer of pure components and binary gas mixtures in adsorbents over a wide frequency range. To demonstrate the capabilities of the apparatus, pressure-swing and volume-swing frequency response experiments were performed in tandem to study transport of pure CO2 in 13X zeolite beads over the frequency range from 10–4 Hz to 10 Hz at pressures from 0.125 to 1 bar. Frequency response spectra show that transport in this system is governed by a nonisothermal macropore diffusion resistance with diffusion occurring by a Knudsen-type mechanism. Macropore diffusion control is confirmed by the existence of particle size dependence of the system’s dynamic response. In smaller zeolite particles, the macropore diffusion resistance is lower, and macropore diffusion becomes less important to the system response. ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie3014204

Reliability-Based Economic Design Optimization of Spread Foundations / Yu Wang in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 7 (Juillet 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 7 (Juillet 2009) . - pp. 954–959 Titre : Reliability-Based Economic Design Optimization of Spread Foundations Type de document : texte imprimé Auteurs : Yu Wang, Auteur Année de publication : 2009 Article en page(s) : pp. 954–959 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Foundation  design  Economic  factors  Costs  Reliability  Uncertainty  principles  Optimization Résumé : This technical note develops a design approach that integrates economic design optimization with reliability-based methodologies to rationally account for geotechnical-related uncertainties. The geotechnical related uncertainties are addressed using a reliability-based approach in the assessment of ultimate limit state (ULS) and serviceability limit state (SLS) requirements. This design approach is illustrated using an example of spread foundation under drained uplift loading. Comparison of the economically optimized design with conventional designs shows that cost of the economically optimized design is lower than that of other feasible designs, and increasing foundation depth is a relatively effective way to increase uplift capacity. Impacts of geotechnical property uncertainties on foundation construction costs are quantified, and the results form a basis of a quantitative cost-benefit analysis of reducing geotechnical property uncertainties. Operative horizontal stress coefficient (K) is shown to be the key parameter that significantly affects the design of a spread foundation under drained uplift, and therefore, deserves attention in site investigation. For a typical allowable uplift displacement ya=25mm , the spread foundation design is dictated by the ULS requirement, and the effect of ya , or SLS requirement, is negligible. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000013 [article] Reliability-Based Economic Design Optimization of Spread Foundations [texte imprimé] / Yu Wang, Auteur . - 2009 . - pp. 954–959. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 7 (Juillet 2009) . - pp. 954–959 Mots-clés : Foundation  design  Economic  factors  Costs  Reliability  Uncertainty  principles  Optimization Résumé : This technical note develops a design approach that integrates economic design optimization with reliability-based methodologies to rationally account for geotechnical-related uncertainties. The geotechnical related uncertainties are addressed using a reliability-based approach in the assessment of ultimate limit state (ULS) and serviceability limit state (SLS) requirements. This design approach is illustrated using an example of spread foundation under drained uplift loading. Comparison of the economically optimized design with conventional designs shows that cost of the economically optimized design is lower than that of other feasible designs, and increasing foundation depth is a relatively effective way to increase uplift capacity. Impacts of geotechnical property uncertainties on foundation construction costs are quantified, and the results form a basis of a quantitative cost-benefit analysis of reducing geotechnical property uncertainties. Operative horizontal stress coefficient (K) is shown to be the key parameter that significantly affects the design of a spread foundation under drained uplift, and therefore, deserves attention in site investigation. For a typical allowable uplift displacement ya=25mm , the spread foundation design is dictated by the ULS requirement, and the effect of ya , or SLS requirement, is negligible. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000013

Reliability index for serviceability limit state of building foundations / Yu Wang in Journal of geotechnical and geoenvironmental engineering, Vol. 134 n°11 (Novembre 2008) 

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