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Response of stiff piles in sand to long-term cyclic lateral loading / C. Leblanc in Géotechnique, Vol. 60 N° 2 (Fevrier 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 2 (Fevrier 2010) . - pp. 79–90 Titre : Response of stiff piles in sand to long-term cyclic lateral loading Type de document : texte imprimé Auteurs : C. Leblanc, Auteur ; Houlsby, G. T., Auteur ; B. W. Byrne, Auteur Année de publication : 2011 Article en page(s) : pp. 79–90 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Stiffness  Piles  Settlement  Repeated  loading  Laboratory  tests  Sands Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The driven monopile is currently the preferred foundation type for most offshore wind farms. While the static capacity of the monopile is important, a safe design must also address issues of accumulated rotation and changes in stiffness after long-term cyclic loading. Design guidance on this issue is limited. To address this, a series of laboratory tests were conducted where a stiff pile in drained sand was subjected to between 8000 and 60 000 cycles of combined moment and horizontal loading. A typical design for an offshore wind turbine monopile was used as a basis for the study, to ensure that pile dimensions and loading ranges were realistic. A complete non-dimensional framework for stiff piles in sand is presented, and applied to interpret the test results. The accumulated rotation was found to be dependent on relative density, and was strongly affected by the characteristics of the applied cyclic load. Particular loading characteristics were found to cause a significant increase in the accumulated rotation. The pile stiffness increased with number of cycles, which contrasts with the current methodology where static load–displacement curves are degraded to account for cyclic loading. Methods are presented to predict the change in stiffness and the accumulated rotation of a stiff pile due to long-term cyclic loading. The use of the methods developed is demonstrated for a typical full-scale monopile. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00196 [article] Response of stiff piles in sand to long-term cyclic lateral loading [texte imprimé] / C. Leblanc, Auteur ; Houlsby, G. T., Auteur ; B. W. Byrne, Auteur . - 2011 . - pp. 79–90. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 2 (Fevrier 2010) . - pp. 79–90 Mots-clés : Stiffness  Piles  Settlement  Repeated  loading  Laboratory  tests  Sands Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : The driven monopile is currently the preferred foundation type for most offshore wind farms. While the static capacity of the monopile is important, a safe design must also address issues of accumulated rotation and changes in stiffness after long-term cyclic loading. Design guidance on this issue is limited. To address this, a series of laboratory tests were conducted where a stiff pile in drained sand was subjected to between 8000 and 60 000 cycles of combined moment and horizontal loading. A typical design for an offshore wind turbine monopile was used as a basis for the study, to ensure that pile dimensions and loading ranges were realistic. A complete non-dimensional framework for stiff piles in sand is presented, and applied to interpret the test results. The accumulated rotation was found to be dependent on relative density, and was strongly affected by the characteristics of the applied cyclic load. Particular loading characteristics were found to cause a significant increase in the accumulated rotation. The pile stiffness increased with number of cycles, which contrasts with the current methodology where static load–displacement curves are degraded to account for cyclic loading. Methods are presented to predict the change in stiffness and the accumulated rotation of a stiff pile due to long-term cyclic loading. The use of the methods developed is demonstrated for a typical full-scale monopile. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.7.00196

Response of stiff piles to random two-way lateral loading / C. Leblanc in Géotechnique, Vol. 60 N° 9 (Septembre 2010) 

Public ISBD [article]  in Géotechnique > Vol. 60 N° 9 (Septembre 2010) . - pp. 715–721 Titre : Response of stiff piles to random two-way lateral loading Type de document : texte imprimé Auteurs : C. Leblanc, Auteur ; B. W. Byrne, Auteur ; Houlsby, G. T., Auteur Année de publication : 2011 Article en page(s) : pp. 715–721 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Settlement  Sands  Deformation  Repeated  loading  Piles  Laboratory  tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : A model for predicting the accumulated rotation of stiff piles under random two-way loading is presented. The model is based on a strain superposition rule similar to Miner's rule and uses rainflow-counting to decompose a random time-series of varying loads into a set of simple load reversals. The method is consistent with the work of LeBlanc et al. (2010) and is supported by 1 g laboratory tests. An example is given for an offshore wind turbine indicating that accumulated pile rotation during the life of the turbine is dominated by the worst expected load. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.09.t.011 [article] Response of stiff piles to random two-way lateral loading [texte imprimé] / C. Leblanc, Auteur ; B. W. Byrne, Auteur ; Houlsby, G. T., Auteur . - 2011 . - pp. 715–721. Génie Civil Langues : Anglais (eng) in Géotechnique > Vol. 60 N° 9 (Septembre 2010) . - pp. 715–721 Mots-clés : Settlement  Sands  Deformation  Repeated  loading  Piles  Laboratory  tests Index. décimale : 624 Constructions du génie civil et du bâtiment. Infrastructures. Ouvrages en terres. Fondations. Tunnels. Ponts et charpentes Résumé : A model for predicting the accumulated rotation of stiff piles under random two-way loading is presented. The model is based on a strain superposition rule similar to Miner's rule and uses rainflow-counting to decompose a random time-series of varying loads into a set of simple load reversals. The method is consistent with the work of LeBlanc et al. (2010) and is supported by 1 g laboratory tests. An example is given for an offshore wind turbine indicating that accumulated pile rotation during the life of the turbine is dominated by the worst expected load. DEWEY : 624.15 ISSN : 0016-8505 En ligne : http://www.icevirtuallibrary.com/content/article/10.1680/geot.09.t.011