Academic literature on the topic 'Soil-pile interaction in liquefiable'

Soil-pile-structure interaction analysis is the simultaneous consideration of the structural frame, pile foundations, and the soil forming the founding material. Failure to consider soil-pile-structure interaction in design will lead to a poor prediction of load distribution within the structure. A poor prediction of load distribution will cause the structure to deform under loads that have not been calculated for. This may result in the structure cracking or the overstressing of columns. If the actual load distribution significantly differs from that designed for, the factor of safety on structural elements may be substantially decreased. Despite the importance, there are currently no studies quantifying the effect of soil-pile-structure interaction for simple office structures. As a result the effects of soil-pile-structure interaction are often deemed unimportant, and ignored in the design of simple structures. Numerical methods are often relied upon to consider soil-pile-structure interaction for complex structures, such as tall towers. However in their current form they are limited because the meshes required for analysis, especially when in three dimensions, are difficult to verify, and take a long time to set up and run. Therefore this thesis proposes a meshing method within the framework of the finite element method that allows large, complex, and non-symmetrical pile foundation layouts to be meshed in a manner that is quick, can be easily checked, and significantly reduces the analysis run time. Application of the meshing method to an office structure (recently designed for the 2012 Olympic Games) has allowed the effects of soil-pile-structure interaction to be quantified. The subsequent normalisation of the results provides a method for assessing when it is necessary to consider soil- pile-structure interaction in future design. Comparison between the monitored performance of 'The Landmark' (a 330m tower founded on a piled raft) and numerical predictions have demonstrated the importance of correct ground stiffness selection for achieving accurate predictions of piled raft settlement, and load distribution. The role of single pile load tests and in situ testing for ground stiffness selection for piled raft design has also been assessed

This research provides validated Finite Element techniques to analyse pile foundations under seismic loads. The results show that the capability of the technique to capture the important pile response which includes kinematic and inertial interaction effects, effects of soil stiffness and depth on pile deflection patterns and permanent deformations.

Il sistema pila-palo è largamente diffuso nelle strutture da ponte grazie ai suoi vantaggi economici e tecnici. Tuttavia questo sistema è fortemente influenzato dagli effetti dell’interazione dinamica terreno-palo-struttura. In aggiunta all’allungamento del periodo fondamentale della struttura, la cedevolezza della fondazione induce una componente rotazionale del moto sismico sul sistema globale che non può essere considerata mediante le comuni procedure di progettazione sismica. Sebbene siano stati sviluppati modelli avanzati per considerare l’interazione terreno-palo-struttura sia in campo lineare e non lineare, i modelli alla Winkler rappresentano uno degli approcci più versatili. In questo lavoro, un modello nonlineare di trave su suolo alla Winkler è stata utilizzato per indagare l’effetto sulla risposta della struttura dei principali aspetti legati al comportamento nonlineare del sistema terreno-fondazione, come ad esempio la plasticizzazione del terreno , la formazione di distacco all’interfaccia palo-terreno, il collasso delle pareti del foro e il degrado o incrudimento ciclico del terreno in prossimità del palo. Sono state eseguite analisi dinamiche incrementali per valutare gli effetti della durata del moto sismico e le non linearità del terreno sulle prestazioni della pila-palo in vari profili di terreno omogeneo e bistrato sia di argilla satura che di sabbia nello stato asciutto o saturo considerando differenti livelli di compattazione. Si è stabilita una procedura per eseguire le analisi dinamiche incrementali considerando gli effetti sia sulla risposta sismica locale sia sulle prestazioni strutturali. Gli effetti dell’interazione cinematica ed inerziale in campo non lineare sono stati analizzati mediante un’ampia indagine parametrica. Le analisi hanno evidenziato il ruolo determinante della componente rotazionale e della durata del moto sismico sulla risposta sismica della pilapalo. I risultati ottenuti sono inoltre stati confrontati con quelli ottenuti mediante un modello lineare. Infine, vengono fatte alcune considerazioni evidenziando le aree grigie della comune pratica di progettazione.<br>Single column bents on extended pile shafts are widely used in bridges for their economical and technical advantages. Nevertheless, this system is strongly affected by Dynamic Soil- Pile-Structure Interaction. In addition to the lengthening of the fundamental period of the structure, the compliance of the foundation induces a rocking component of the seismic motion experienced by the overall system that cannot be considered by following the procedures of a common seismic design practice. Although advanced models have been developed in order to account for Soil-Pile-Structure Interaction both in the linear and nonlinear range, Winkler-type models represent one of the most feasible approaches. In this work, a Beam on Nonlinear Winkler Foundation model is used to investigate the importance of features typical in soil nonlinear behaviour such as yielding, gapping, soil cave-in and cyclic hardening/degradation effects on the performance of extended pile shafts. A procedure to estimate the model parameters from geotechnical soil characterization is presented. Incremental Dynamic Analyses are performed to evaluate the effects of Ground Motion Duration and soil nonlinearity on the performance of extended pile shafts in various homogeneous and two-layered soil profiles, including saturated clay and sand in either fully dry or saturated state with different levels of compaction. A procedure to perform Incremental Dynamic Analysis, including effects on both site response analysis and on the structural performance, is established. Nonlinear kinematic and inertial interaction effects are analyzed by means of an exhaustive parametric investigation. The significant effects of the rocking component and the Ground Motion Duration on the seismic response of extended pile shafts are demonstrated. Comparisons with results obtained with a linear model are also presented. Finally, some considerations are drawn pointing out grey areas of the common design practice.