• Sciences de l'ingénieur/Mécanique/Vibrations
  
• Sciences de l'ingénieur/Mécanique/Mécanique des structures
  
• Sciences de l'ingénieur/Autre
  

Cet article présente des travaux effectués sur le bâtiment expérimental de l'IUT de Nîmes. L'objectif est d'analyser finement le comportement énergétique du bâtiment mais aussi des systèmes d'éclairage, de chauffage, de ventilation et d'ECS en fonction des sollicitations extérieures (météo) et du pilotage des systèmes du bâtiment qui simulent le comportement de l'occupant. Le chauffage du bâtiment expérimental est assuré par un plancher chauffant alimenté par une pompe à chaleur monobloc air-eau de 6 kW. Cet article porte seulement sur l'étude énergétique de la pompe à chaleur, effectué sur 3 périodes hivernales de 5 jours avec 3 scénarios de fonctionnement différents : Chauffage + ECS avec volets ouverts, chauffage seul avec et sans volets ouverts. Ce travail nous a permis de définir les outils d'instrumentation, de pilotage et d'acquisitions nécessaires à l'évaluation de l'impact de l'occupant sur le comportement énergétique du bâtiment à travers le chauffage, le rafraichissement, la ventilation, la consommation d'ECS et la gestion des ouvrants.

Tensegrity systems are self stressed reticulate structures composed of a set of compressed struts assembled inside a continuum of tendons. This principle is at the origin of lightweight and transparent structures that can cover large spaces and be erected, in particular cases, by deployment. In this paper, we propose a general design and optimization procedure adapted to modular structures following this principle. An application is presented on the case of a curved deployable footbridge.Besides, as lightweight frames, these systems are subject to deformation and vibration issues when faced to varying actions such as climatic, human, orseismic loads. Active control is as solution that allows, using actuators integrated into the structure, to attenuate these effects. On the case of a real plane modular tensegrity grid, we present a specific methodology for the active damping of the first two modes and its experimental validation.

A new conceptual design for the architecture of a large deployable space reflector is presented. The reflective parabolic surface is made of a mesh shaped by a cable net and the supporting rim structure is based on scissor mechanisms associated with flexible joints. These joints replace complex articulations while allowing the storage of the energy required for deployment. They also affect the stiffness of the structure and the tension of the cable net. The dynamic behavior was studied by finite element modeling and through tests on an experimental prototype with a gravity compensation device. We focused on the first natural mode, which is an important design criterion for space applications. The measurements are compared to simulation results and we discuss the influence of suspension threads and gravity in the model.

The structures of tensegrity are light structures of which stability is conditioned in a state of prestressing called self-stress. Work presented relates to a structure with double layer which is instrumented with gauges of deformation to determine the forces in the bars. The aim of work is to find the forces in the elements by indirect measurement for further in-situ applications when the bars instrumentations will be impossible. Here, we explore the possibility of using the measurement of the fields of acceleration of the nodes of a structure of tensegrity under dynamic loading in order to identify the self-stress state. We show the effect of the self-stress level on the modes of vibration of the structure to determine the correlation between the precision of this identification and the influence of the mode concerned. The results confirm the complex relation which exists between the Eigen-modes and the identification of self-stress state. The identification is generally more powerful for the first global modes which are impacted by all self-stress states than for the local modes which are often dependent only of one self-stress state.