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Impact of toe resistance in reinforced masonry block walls / Leshchinsky, Dov in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 2 (Fevrier 2012) . - pp. 236-240 Titre : Impact of toe resistance in reinforced masonry block walls : Design dilemma Type de document : texte imprimé Auteurs : Leshchinsky, Dov, Auteur ; Farshid Vahedifard, Auteur Année de publication : 2012 Article en page(s) : pp. 236-240 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Mechanically  stabilized  earth  (MSE)  walls  Geosynthetic  reinforced  walls  Retaining  walls  Stability  Limit  equilibrium Résumé : Reinforced masonry block retaining walls are comprised of a narrow column of stacked blocks at their exposed end. This column is placed on a nonstructural leveling pad to facilitate the placement of facing units. Theoretically, this column can generate very large toe resistance to sliding. A recent publication indicates that an accepted design methodology implicitly counts on this resistance in assessing the reinforcement load. Although not calculated in this design, it unconditionally considers that over 60% of the resultant horizontal force in a 12-m-high wall is carried by the toe, which is made up of 0.3-m-deep blocks. This paper elucidates this issue by explicitly identifying the magnitude of toe resistance and critically reviews whether such high resistance is universally suitable for design. It shows that high toe resistance may not be feasible for most foundation soils. The high impact of toe resistance on the reinforcement force poses a design dilemma as to the reliability of this resistance, even if attainable. Practically, the leveling pad is not intended to serve as a critical structural element and thus should not be relied on for maintaining the toe resistance in long-term design. Economically, ignoring the toe resistance has little impact on the overall cost. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i2/p236_s1?isAuthorized=no [article] Impact of toe resistance in reinforced masonry block walls : Design dilemma [texte imprimé] / Leshchinsky, Dov, Auteur ; Farshid Vahedifard, Auteur . - 2012 . - pp. 236-240. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 2 (Fevrier 2012) . - pp. 236-240 Mots-clés : Mechanically  stabilized  earth  (MSE)  walls  Geosynthetic  reinforced  walls  Retaining  walls  Stability  Limit  equilibrium Résumé : Reinforced masonry block retaining walls are comprised of a narrow column of stacked blocks at their exposed end. This column is placed on a nonstructural leveling pad to facilitate the placement of facing units. Theoretically, this column can generate very large toe resistance to sliding. A recent publication indicates that an accepted design methodology implicitly counts on this resistance in assessing the reinforcement load. Although not calculated in this design, it unconditionally considers that over 60% of the resultant horizontal force in a 12-m-high wall is carried by the toe, which is made up of 0.3-m-deep blocks. This paper elucidates this issue by explicitly identifying the magnitude of toe resistance and critically reviews whether such high resistance is universally suitable for design. It shows that high toe resistance may not be feasible for most foundation soils. The high impact of toe resistance on the reinforcement force poses a design dilemma as to the reliability of this resistance, even if attainable. Practically, the leveling pad is not intended to serve as a critical structural element and thus should not be relied on for maintaining the toe resistance in long-term design. Economically, ignoring the toe resistance has little impact on the overall cost. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i2/p236_s1?isAuthorized=no

Relationship between the seismic coefficient and the unfactored geosynthetic force in reinforced earth structures / Farshid Vahedifard in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 10 (Octobre 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 10 (Octobre 2012) . - pp.1209–1221. Titre : Relationship between the seismic coefficient and the unfactored geosynthetic force in reinforced earth structures Type de document : texte imprimé Auteurs : Farshid Vahedifard, Auteur ; Leshchinsky, Dov, Auteur ; Christopher L. Meehan, Auteur Année de publication : 2013 Article en page(s) : pp.1209–1221. Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Soil  stabilization  Geosynthetics  Seismic  design  Limit  equilibrium  Earthquakes Résumé : This paper presents an integrated analytical method for calculating the resultant unfactored geosynthetic force in reinforced earth structures under seismic loading conditions. The method utilizes a pseudostatic limit equilibrium approach for assessing the internal stability of a reinforced earth structure, assuming a potential rotational failure along a log spiral trace. A closed-form solution is presented for determining the sum of all horizontal forces mobilized in the geosynthetic reinforcement along their intersection with the critical log spiral surface. This mobilized sum is then redistributed among the individual layers to determine the unfactored reinforcement forces that are needed to resist the applied seismic acceleration. Parametric studies were utilized, and the results are presented in a series of design charts for different conditions. Such charts can be used to determine the required tensile strength of the reinforcement for a given seismic coefficient. Alternatively, for a given reinforcement strength, the formulation can also be used to determine the yield acceleration that is required for calculating seismic displacements. An advantage of the proposed methodology is that it determines the yield acceleration caused by rotation of the reinforced mass (internal stability), which allows for a rational, yet simple, assessment of the displacement related to the internal movement of the reinforced mass. The design charts illustrate the effect of earth structure backslope and the vertical seismic coefficient. The results also show the impact of the assumed location of the resultant reinforcement force under seismic loading conditions. Variations in the location of this force over a reasonable range have little impact on the results. The inclination of the backslope has a significant effect for earth structures with smaller batters and/or larger horizontal seismic coefficients. Additionally, vertical seismic coefficients with a downward direction increase the mobilized force in the geosynthetic reinforcement. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000701 [article] Relationship between the seismic coefficient and the unfactored geosynthetic force in reinforced earth structures [texte imprimé] / Farshid Vahedifard, Auteur ; Leshchinsky, Dov, Auteur ; Christopher L. Meehan, Auteur . - 2013 . - pp.1209–1221. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 10 (Octobre 2012) . - pp.1209–1221. Mots-clés : Soil  stabilization  Geosynthetics  Seismic  design  Limit  equilibrium  Earthquakes Résumé : This paper presents an integrated analytical method for calculating the resultant unfactored geosynthetic force in reinforced earth structures under seismic loading conditions. The method utilizes a pseudostatic limit equilibrium approach for assessing the internal stability of a reinforced earth structure, assuming a potential rotational failure along a log spiral trace. A closed-form solution is presented for determining the sum of all horizontal forces mobilized in the geosynthetic reinforcement along their intersection with the critical log spiral surface. This mobilized sum is then redistributed among the individual layers to determine the unfactored reinforcement forces that are needed to resist the applied seismic acceleration. Parametric studies were utilized, and the results are presented in a series of design charts for different conditions. Such charts can be used to determine the required tensile strength of the reinforcement for a given seismic coefficient. Alternatively, for a given reinforcement strength, the formulation can also be used to determine the yield acceleration that is required for calculating seismic displacements. An advantage of the proposed methodology is that it determines the yield acceleration caused by rotation of the reinforced mass (internal stability), which allows for a rational, yet simple, assessment of the displacement related to the internal movement of the reinforced mass. The design charts illustrate the effect of earth structure backslope and the vertical seismic coefficient. The results also show the impact of the assumed location of the resultant reinforcement force under seismic loading conditions. Variations in the location of this force over a reasonable range have little impact on the results. The inclination of the backslope has a significant effect for earth structures with smaller batters and/or larger horizontal seismic coefficients. Additionally, vertical seismic coefficients with a downward direction increase the mobilized force in the geosynthetic reinforcement. ISSN : 1090-0241 En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29GT.1943-5606.0000701