La Terre est une planète en constante évolution et sa surface ne cesse de se transformer. Ses déformations soulèvent des questionnements. Depuis plusieurs années, le L2G de l’ESGT s’intéresse à l’étude des déformations par inter comparaison de techniques. Il dispose en cela de différents procédés de mesure. Puis au fil du temps, le laboratoire s’interroge sur l’intérêt de réaliser une combinaison entre différentes techniques de mesure afin d’observer des déformations fines et précises (quelques millimètres).L’objectif de cette thèse est de démontrer l’intérêt de combiner des mesures GNSS et des mesures topométriques, celles-ci semblant être les plus utilisées, et de les concrétiser. Les résultats présentés sont basés sur des simulations et sur des campagnes de mesures combinées des techniques de GNSS et de topométrie effectuée sur un réseau test d’une étendue locale. Les calculs évoluent en fonction de la distance de la ligne de base et en modifiant les durées de sessions de mesures. Nous montrons qu’une combinaison par cumul des équations normales améliore la précision du positionnement non seulement par rapport à l’utilisation de chaque technique séparée, mais également par rapport aux méthodes classiques basées sur la combinaison des coordonnées issues des techniques de GNSS et de topométrie. / The Earth is a constantly evolving planet and its surface keeps transforming. Its deformations raise questions. For several years, the L2G at ESGT has been interested in the study of deformations through inter comparison of techniques. For this, it has various measurement processes. Then, with time, the laboratory is now pondering about the interest of combining various techniques of measurement in order to observe fine and precise deformations (a few millimeters).The aim of this PhD thesis is to demonstrate the interest of combining GNSS and topometric measurements, the latter being apparently the most commonly used. The presented results are based on simulations and campaigns of combined measurement through the use of GNSS and topometric techniques made on a model network of a local area. Thecalculations made are dependent both on the distance of the baseline and the alteration of the session length.We show that a combination through the accumulation of the normal equations improves the localisation accuracy regarding not only the use of every separate technique but also the more classic methods based on the coordinates combination provided by GNSS and topometric techniques.

Indiana University-Purdue University Indianapolis (IUPUI) / Crashworthiness design is gaining more importance in the automotive industry due to high competition and tight safety norms. Further there is a need for light weight structures in the automotive design. Structural optimization in last two decades have been widely explored to improve existing designs or conceive new designs with better crashworthiness and reduced mass. Although many gradient based and heuristic methods for topology and topometry based crashworthiness design are available these days, most of them result in stiff structures that are suitable only for a set of vehicle components in which maximizing the energy absorption or minimizing the intrusion is the main concern. However, there are some other components in a vehicle structure that should have characteristics of both stiffness and flexibility. Moreover, the load paths within the structure and potential buckle modes also play an important role in efficient functioning of such components. For example, the front bumper, side frame rails, steering column, and occupant protection devices like the knee bolster should all exhibit controlled deformation and collapse behavior. This investigation introduces a methodology to design dynamically crushed thin-walled tubular structures for crashworthiness applications. Due to their low cost, high energy absorption efficiency, and capacity to withstand long strokes, thin-walled tubular structures are extensively used in the automotive industry. Tubular structures subjected to impact loading may undergo three modes of deformation: progressive crushing/buckling, dynamic plastic buckling, and global bending or Euler-type buckling. Of these, progressive buckling is the most desirable mode of collapse because it leads to a desirable deformation characteristic, low peak reaction force, and higher energy absorption efficiency. Progressive buckling is generally observed under pure axial loading; however, during an actual crash event, tubular structures are often subjected to oblique impact loads in which Euler-type buckling is the dominating mode of deformation. This undesired behavior severely reduces the energy absorption capability of the tubular structure. The design methodology presented in this paper relies on the ability of a compliant mechanism to transfer displacement and/or force from an input to desired output port locations. The suitable output port locations are utilized to enforce desired buckle zones, mitigating the natural Euler-type buckling effect. The problem addressed in this investigation is to find the thickness distribution of a thin-walled structure and the output port locations that maximizes the energy absorption while maintaining the peak reaction force at a prescribed limit. The underlying design for thickness distribution follows a uniform mutual potential energy density under a dynamic impact event. Nonlinear explicit finite element code LS-DYNA is used to simulate tubular structures under crash loading. Biologically inspired hybrid cellular automaton (HCA) method is used to drive the design process. Results are demonstrated on long straight and S-rail tubes subject to oblique loading, achieving progressive crushing in most cases.