Seismic earthquakes are a real danger for the construction evolution of high rise buildings. The rate of earthquakes around the world is noteworthy in a wide range of construction areas. In this study, we present the dynamic behavior of a high-rise RC building with dynamic isolators (lead-rubber-bearing), in comparison with a traditional shear wall system of the same building. Seismic isolation has been introduced in building construction to increase the structural stability and to protect the non-structural components against the damaging effects of an earthquake. In order to clarify the influence of incorporating lead rubber bearing isolators in the seismic response and in reducing seismic damages; a comparative study is performed between a fixed base system (shear wall system) and an isolated base system (Lead Rubber Bearing) on an irregular high rise reinforced concrete (RC) building located in Beirut consisting of 48 storeys almost asymmetric orthogonally. For this purpose, a non-linear analysis of a real earthquake acceleration record (EI Centro seismic signal) is conducted, so that the mode shapes, the damping ratio and the natural frequencies of the two models are obtained using ETABS software. The results prove a substantial elongation of the building period, as well as a reduction in the building displacement, the roof acceleration, the inter-storey drift ratio and the base shear force of isolated building relative to fixed-base building. This study proves that this technology is applicable to high rise buildings with acceptable results.

Due to the complex microstructure of textile composites, the modeling of physical properties is challenging. The mechanical properties of textiles depend on different geometrical parameters such as the yarn's geometrical properties, undulation, geometrical cross-section, gap between two adjacent yarns, and other parameters. In this paper, a geometrical modeling of 2D and 3D woven composites is presented. The novelty of this paper is related to a more realistic modeling of yarn's cross-section. The presented modeling technique takes into account that yarns constituting 2D or 3D woven composite do not have the same cross-section shape and undulated part as usually considered with an ideal unit cell modeling. The proposed technique leads to calculate the fiber volume fraction of yarns, then the fiber volume fraction of the unit cell of the studied composite. It was applied to different kinds of woven composites where the modeled unit cell converged to a more realistic shape.

The vibrations behavior analysis is an essential step in the mechanical design process. Several methods such as analytical modelling, numerical analysis and experimental measurements can be used for this purpose. However, the numerical or analytical models should be validated through experimental measurements, usually expensive. This paper introduces an inexpensive smartphone as an accurate, non-intrusive vibrations’ behavior measurement device. An experimental measurement procedure based on the video processing method is presented. This procedure allows the measurement of the natural frequencies and the mode shapes of a vibrating structure, simply by using a smartphone built-in camera. The experimental results are compared to those obtained using an accurate analytical model, where the natural frequencies error is less than 2.7% and the modal assurance criterion is higher than 0.89. In order to highlight the obtained results, a comparison has been done using a high quality and high frame per second (fps) camera-based measurement of material properties. Since the highest recovered natural frequency and its associated mode shape depend on the frame per second rate of the recorded video, this procedure has great potential in low frequencies problems such as for big structures like buildings and bridges. This validated technique re-introduces the personal smartphone as an accurate inexpensive non-contacting vibration measurement tool.

Dans le contexte des moteurs électriques automobiles, les phénomènes vibratoires d'origine magnétique soulèvent une problématique relativement récente. L'objectif de cette thèse est la mise au point d'un modèle multi-physique pertinent d'une machine électrique afin de réaliser quelques études spécifiques, d'optimiser la machine et de prendre en compte la variabilité du comportement vibratoire. La modélisation numérique s'appuie totalement sur des formulations analytiques afin de bien maîtriser les différentes physiques. Des mesures expérimentales sur la machine permettent une confrontation avec le modèle numérique multi-physique et une validation des choix de modélisation. Dans ce contexte de modélisation multi-physique, un outil de couplage est développé entre les modèles 2D électromagnétique et 3D mécanique afin d'évaluer les comportements vibratoires d'origine électromagnétique de la machine. Une attention particulière a été portée à la prise en compte des forces magnétiques radiales et surtout tangentielles sur le stator de la machine électrique. Une méthode d'optimisation, basée sur le principe d'une surface de réponse dynamique, est appliquée sur le modèle électromagnétique afin d'améliorer des paramètres de conception de la machine. Les incertitudes liées à la conception sont souvent nombreuses, notamment dans le domaine vibratoire. A cet effet, la méthode MSP (Modal Stability Procedure) prenant en compte la variabilité des paramètres matériaux est proposée. La formulation MSP pour l'élément 3D hexaédrique est développée et appliquée au stator électrique afin d'évaluer la variabilité des fréquences propres et des fonctions de réponse en fréquence.