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Lateral performance of full-scale bridge abutment wall with granular backfill / Anne Lemnitzer in Journal of geotechnical and geoenvironmental engineering, Vol. 135 N° 4 (Avril 2009) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 4 (Avril 2009) . - pp. 506–514 Titre : Lateral performance of full-scale bridge abutment wall with granular backfill Type de document : texte imprimé Auteurs : Anne Lemnitzer, Auteur ; Eric R. Ahlberg, Auteur ; Robert L. Nigbor, Auteur Année de publication : 2009 Article en page(s) : pp. 506–514 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Bridge  abutments  Passive  pressure  Seismic  design  Lateral  pressure  Backfills  Granular  materials Résumé : Bridge abutments typically contain a backwall element that is designed to break free of its base support when struck by a bridge deck during an earthquake event and push into the abutment backfill soils. Results are presented for a full-scale cyclic lateral load test of an abutment backwall configured to represent the dimensions ( 1.7m height), boundary conditions, and backfill materials (compacted silty sand) that are typical of California bridge design practice. An innovative loading system was utilized that operates under displacement control and that assures horizontal wall displacement with minimal vertical displacement. The applied horizontal displacement ranged from null to approximately 11% of the wall height (0.11H) . The maximum earth pressure occurred at a wall displacement of 0.03H and corresponded to a passive earth pressure coefficient of Kp=16.3 . The measured force distribution applied to the wall from hydraulic actuators allowed the soil pressure distribution to be inferred as triangular in shape and the mobilized wall-soil interface friction to be evaluated as approximately one-third to one-half of the soil friction angle. Post-test trenching of the backfill showed a log-spiral principal failure surface at depth with several relatively minor shear surfaces further up in the passive wedge. The ultimate passive resistance is well estimated by the log-spiral method and a method of slices approach. The shape of the load-deflection relationship is well estimated by models that produce a hyperbolic curve shape. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A4%2850 [...] [article] Lateral performance of full-scale bridge abutment wall with granular backfill [texte imprimé] / Anne Lemnitzer, Auteur ; Eric R. Ahlberg, Auteur ; Robert L. Nigbor, Auteur . - 2009 . - pp. 506–514. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 135 N° 4 (Avril 2009) . - pp. 506–514 Mots-clés : Bridge  abutments  Passive  pressure  Seismic  design  Lateral  pressure  Backfills  Granular  materials Résumé : Bridge abutments typically contain a backwall element that is designed to break free of its base support when struck by a bridge deck during an earthquake event and push into the abutment backfill soils. Results are presented for a full-scale cyclic lateral load test of an abutment backwall configured to represent the dimensions ( 1.7m height), boundary conditions, and backfill materials (compacted silty sand) that are typical of California bridge design practice. An innovative loading system was utilized that operates under displacement control and that assures horizontal wall displacement with minimal vertical displacement. The applied horizontal displacement ranged from null to approximately 11% of the wall height (0.11H) . The maximum earth pressure occurred at a wall displacement of 0.03H and corresponded to a passive earth pressure coefficient of Kp=16.3 . The measured force distribution applied to the wall from hydraulic actuators allowed the soil pressure distribution to be inferred as triangular in shape and the mobilized wall-soil interface friction to be evaluated as approximately one-third to one-half of the soil friction angle. Post-test trenching of the backfill showed a log-spiral principal failure surface at depth with several relatively minor shear surfaces further up in the passive wedge. The ultimate passive resistance is well estimated by the log-spiral method and a method of slices approach. The shape of the load-deflection relationship is well estimated by models that produce a hyperbolic curve shape. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282009%29135%3A4%2850 [...]

Nonlinear efficiency of bored pile group under lateral loading / Anne Lemnitzer in Journal of geotechnical and geoenvironmental engineering, Vol. 136 N° 12 (Décembre 2010) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 12 (Décembre 2010) . - pp. 1673-1685 Titre : Nonlinear efficiency of bored pile group under lateral loading Type de document : texte imprimé Auteurs : Anne Lemnitzer, Auteur ; Payman Khalili-Tehrani, Auteur ; Eric R. Ahlberg, Auteur Année de publication : 2011 Article en page(s) : pp. 1673-1685 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Pile  groups  Piers  Pile  lateral  loads  Soil-structure  interaction Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A 3×3 bored pile group consisting of nine cast-in-drilled-hole reinforced concrete shafts and a comparable single-shaft were subjected to reversed cyclic, lateral head loading to investigate group interaction effects across a wide range of lateral displacements. The piles had the same diameter of d = 0.61 m and similar soil conditions; however, various equipment constraints led to two differences: (1) a fixed head (zero rotation) boundary condition for the single pile versus minor pile cap rotation in the vertical plane for the group and (2) shaft longitudinal reinforcement ratios of 1.8% for the single pile and 1% for the group piles. To enable comparisons between the test results, a calibrated model of the single pile (1.8% reinforcement) was developed and used to simulate the response of a single shaft with 1% reinforcement. Additional simulations of the pile group were performed to evaluate the effects of cap rotation on group response. By comparing the simulated responses for common conditions, i.e., 1% reinforcing ratio and zero head rotation, group efficiencies were found to range from unity at lateral displacements <0.004×d to 0.8 at small displacements ∼ 0.01–0.02×d and up to 0.9 at failure (displacements >0.04×d). Hence, we find that group efficiency depends on the level of nonlinearity in the foundation system. The general group efficiency, although not its displacement-dependence, is captured by p-multipliers in the literature for reinforced concrete, fixed-head piles. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i12/p1673_s1?isAuthorized=no [article] Nonlinear efficiency of bored pile group under lateral loading [texte imprimé] / Anne Lemnitzer, Auteur ; Payman Khalili-Tehrani, Auteur ; Eric R. Ahlberg, Auteur . - 2011 . - pp. 1673-1685. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 136 N° 12 (Décembre 2010) . - pp. 1673-1685 Mots-clés : Pile  groups  Piers  Pile  lateral  loads  Soil-structure  interaction Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A 3×3 bored pile group consisting of nine cast-in-drilled-hole reinforced concrete shafts and a comparable single-shaft were subjected to reversed cyclic, lateral head loading to investigate group interaction effects across a wide range of lateral displacements. The piles had the same diameter of d = 0.61 m and similar soil conditions; however, various equipment constraints led to two differences: (1) a fixed head (zero rotation) boundary condition for the single pile versus minor pile cap rotation in the vertical plane for the group and (2) shaft longitudinal reinforcement ratios of 1.8% for the single pile and 1% for the group piles. To enable comparisons between the test results, a calibrated model of the single pile (1.8% reinforcement) was developed and used to simulate the response of a single shaft with 1% reinforcement. Additional simulations of the pile group were performed to evaluate the effects of cap rotation on group response. By comparing the simulated responses for common conditions, i.e., 1% reinforcing ratio and zero head rotation, group efficiencies were found to range from unity at lateral displacements <0.004×d to 0.8 at small displacements ∼ 0.01–0.02×d and up to 0.9 at failure (displacements >0.04×d). Hence, we find that group efficiency depends on the level of nonlinearity in the foundation system. The general group efficiency, although not its displacement-dependence, is captured by p-multipliers in the literature for reinforced concrete, fixed-head piles. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v136/i12/p1673_s1?isAuthorized=no