Study On An Elasto-plastic Macro-element Method For The Analysis Of A Bucket Foundation

Currently,many studies are being carried out with the aim of making renewable energy sources available to the population.And a large number of studies are oriented to the field of wind energy where researches are being conducted all over the world to make this area even more profitable.An important branch of wind energy work concerns the installation of wind turbines.Investigations made it possible to have more and more optimal installation methods and procedures for the installation of wind turbines in general and particularly for offshore wind turbines.This is mainly about the types of foundations used to get optimal installation process.The bucket foundation technology is a particular case of foundations with multiple applications and whose use as a foundation for offshore wind turbines is growing.Taking into account the geotechnical,hydrological and logistical requirements,bucket foundations are becoming a good alternative for the installation of offshore wind turbines.This is how their study interested several authors who worked on their design,analysis and installation.In this particular case of bucket foundation analysis,the new method known as the macro-element method is nowadays a very powerful tool.The present thesis will deal with a macro-element model for the analysis of bucket foundations.The analysis will use a 2D and three degrees of freedom model to highlight certain details with regard to the application of macro-elements for the analysis of bucket foundations.Details concerning the bearing capacity,the calculation of the displacements induced by the applied loading system,the influence of the ratio of the caisson length to its diameter(aspect ratio)and the influence of the type of soil will be given.Some time ago,the macro-element method was only used to get approximate responses of a soil-structure interaction under a given loading system and Its only advantage was that it considerably reduced the time required for analysis,nowadays,it is establishing itself as a reliable tool able to compete with traditional methods including that of finite elements and this for different types of structures and constraints related to them.The macro-element method presented in this thesis is based on an elasto-plastic analysis to study the material non-linearities that can be observed on a soil-structure system when it is subjected to the action of a loading system.So,the present work will make a good choice of elasto-plastic analysis tools that are: the loading surface,plastic potential,the flow rule and the hardening rule.The total response of the system is actually made of elastic and plastic parts but also of deformations induced by geometrical nonlinearities,so a study of the uplift will be roughly presented just to highlight some details related to this phenomenon.The analysis of the caisson model by the macro-element method will be conducted with the use of the software MATLAB with which,existing models will be analyzed.The analysis will consist in determining the way in which the responses vary with the geometry of the caisson given by the aspect ratio,and the variation of the responses with the applied load system.The caisson rotates about a point whose position deserves to be determined with respect to a reference or particularly with respect to the load reference point(LRP).The procedure is especially important for bucket foundations to install,as it also enables to conduct a quick and rough design using trial and error procedure.