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Axial compression of footings in cohesionless soils. I: load-settlement behavior / Sami O. Akbas in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 11 (Novembre 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 11 (Novembre 2009) . - pp. 1562–1574 Titre : Axial compression of footings in cohesionless soils. I: load-settlement behavior Type de document : texte imprimé Auteurs : Sami O. Akbas, Auteur ; Fred H. Kulhawy, Auteur Année de publication : 2009 Article en page(s) : pp. 1562–1574 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : FootingsLoad  testsFoundation  settlementCohesionless  soilsSoil  compression Résumé : The results of 167 full-scale field load tests were used to examine several issues related to the load-displacement behavior of footings in cohesionless soils under axial compression loading, including (1) method to interpret the “failure load” from the load-settlement curves; (2) correlations among interpreted loads and settlements; and (3) generalized load-settlement behavior. The L1-L2 method was found to be more appropriate than the “tangent intersection” and “10% of the footing width” methods for interpreting the failure load. The interpreted loads and displacements indicate that footing load-settlement behavior is less elastic and more nonlinear than that of drilled foundations. The results show that the footing behavior will be beyond the elastic limit for designs where a traditional factor of safety between 2 and 3 is used. A normalized curve was developed by approximating the load-settlement curve for each load test in the database by hyperbolic fitting, and the uncertainty in this curve was quantified. This normalized curve can be used in footing design that considers capacity and settlement together. Where possible or warranted, the normalized curve can be subdivided as a function of initial soil modulus. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000135 [article] Axial compression of footings in cohesionless soils. I: load-settlement behavior [texte imprimé] / Sami O. Akbas, Auteur ; Fred H. Kulhawy, Auteur . - 2009 . - pp. 1562–1574. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 11 (Novembre 2009) . - pp. 1562–1574 Mots-clés : FootingsLoad  testsFoundation  settlementCohesionless  soilsSoil  compression Résumé : The results of 167 full-scale field load tests were used to examine several issues related to the load-displacement behavior of footings in cohesionless soils under axial compression loading, including (1) method to interpret the “failure load” from the load-settlement curves; (2) correlations among interpreted loads and settlements; and (3) generalized load-settlement behavior. The L1-L2 method was found to be more appropriate than the “tangent intersection” and “10% of the footing width” methods for interpreting the failure load. The interpreted loads and displacements indicate that footing load-settlement behavior is less elastic and more nonlinear than that of drilled foundations. The results show that the footing behavior will be beyond the elastic limit for designs where a traditional factor of safety between 2 and 3 is used. A normalized curve was developed by approximating the load-settlement curve for each load test in the database by hyperbolic fitting, and the uncertainty in this curve was quantified. This normalized curve can be used in footing design that considers capacity and settlement together. Where possible or warranted, the normalized curve can be subdivided as a function of initial soil modulus. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000135

Axial compression of footings in cohesionless soils. II: bearing capacity / Sami O. Akbas in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 11 (Novembre 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 11 (Novembre 2009) . - pp. 1575–1582 Titre : Axial compression of footings in cohesionless soils. II: bearing capacity Type de document : texte imprimé Auteurs : Sami O. Akbas, Auteur ; Fred H. Kulhawy, Auteur Année de publication : 2009 Article en page(s) : pp. 1575–1582 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : FootingsLoad  testsFoundation  settlementCohesionless  soilsSoil  compressionLoad  bearing  capacity Résumé : An extensive database of full-scale field load tests was used to examine the bearing capacity for footings in cohesionless soils. Each load test curve was evaluated consistently to determine the interpreted failure load (i.e., bearing capacity) using the L1-L2 method. This test value then was compared with the theoretical bearing capacity, computed primarily using the basic Vesić model. The comparisons show that, for footing widths B>1 m , the field results agree very well with the Vesić predictions. However, for B<1 m , the results indicated a relationship between B and the predicted-to-measured bearing capacity ratio. Accordingly, a simple modification was made to the bearing capacity equation, and the resulting predictions are very good. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000136 [article] Axial compression of footings in cohesionless soils. II: bearing capacity [texte imprimé] / Sami O. Akbas, Auteur ; Fred H. Kulhawy, Auteur . - 2009 . - pp. 1575–1582. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 11 (Novembre 2009) . - pp. 1575–1582 Mots-clés : FootingsLoad  testsFoundation  settlementCohesionless  soilsSoil  compressionLoad  bearing  capacity Résumé : An extensive database of full-scale field load tests was used to examine the bearing capacity for footings in cohesionless soils. Each load test curve was evaluated consistently to determine the interpreted failure load (i.e., bearing capacity) using the L1-L2 method. This test value then was compared with the theoretical bearing capacity, computed primarily using the basic Vesić model. The comparisons show that, for footing widths B>1 m , the field results agree very well with the Vesić predictions. However, for B<1 m , the results indicated a relationship between B and the predicted-to-measured bearing capacity ratio. Accordingly, a simple modification was made to the bearing capacity equation, and the resulting predictions are very good. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000136

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 [...]

Evaluation of uplift interpretation criteria for drilled shaft capacity / Yit-Jin Chen in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°10 (Octobre 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°10 (Octobre 2008) . - pp. 1459–1468 Titre : Evaluation of uplift interpretation criteria for drilled shaft capacity Type de document : texte imprimé Auteurs : Yit-Jin Chen, Auteur ; Hsin-Wen Chang, Auteur ; Fred H. Kulhawy, Auteur Année de publication : 2008 Article en page(s) : pp. 1459–1468 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Drilled  shafts  Foundations  Uplift  Load  tests  Displacement Résumé : Representative interpretation criteria are examined to evaluate the capacity of drilled shaft foundations under axial uplift loading. A wide variety of uplift load test data are used, and these data are divided into drained and undrained databases. The interpretation criteria are applied to these load test data to establish a consistent uplift interpretation criterion. The results are comparable for both drained and undrained loading. In general, the undrained load test results show somewhat less variability than the drained results. Based on these analyses, the QL2 , Q0.5in , and slope tangent methods are the more reliable and consistent, and specific design recommendations for the interpretation of uplift drilled shaft load test are given, in terms of both capacity and displacement. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A10%281 [...] [article] Evaluation of uplift interpretation criteria for drilled shaft capacity [texte imprimé] / Yit-Jin Chen, Auteur ; Hsin-Wen Chang, Auteur ; Fred H. Kulhawy, Auteur . - 2008 . - pp. 1459–1468. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°10 (Octobre 2008) . - pp. 1459–1468 Mots-clés : Drilled  shafts  Foundations  Uplift  Load  tests  Displacement Résumé : Representative interpretation criteria are examined to evaluate the capacity of drilled shaft foundations under axial uplift loading. A wide variety of uplift load test data are used, and these data are divided into drained and undrained databases. The interpretation criteria are applied to these load test data to establish a consistent uplift interpretation criterion. The results are comparable for both drained and undrained loading. In general, the undrained load test results show somewhat less variability than the drained results. Based on these analyses, the QL2 , Q0.5in , and slope tangent methods are the more reliable and consistent, and specific design recommendations for the interpretation of uplift drilled shaft load test are given, in terms of both capacity and displacement. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A10%281 [...]

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

Identification and description of soils containing very coarse fractions / Fred H. Kulhawy in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 5 (Mai 2009) 

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Reliability-based design approach for differential settlement of footings on cohesionless soils / Sami O. Akbas in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 12 (Décembre 2009) 

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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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