Projet de thèse en Génie Civil
Sous la direction de Jean-François Caron.
Thèses en préparation à Paris Est en cotutelle avec l'Université de Stuttgart , dans le cadre de SIE - Sciences, Ingénierie et Environnement , en partenariat avec NAVIER (laboratoire) depuis le 14-12-2012 .
New design strategy for freeform structures in CFRP concrete
The desire to generate free form structures in architecture is large, but in most cases a cost-effective implementation is difficult and the quality of execution of such projects suffers. This is due to the fact that the implementation of supporting structure with traditional materials and design principles are difficult. For free-formed steel structures, the costs of forming plates or sections are very high. Moreover, the standard design-concept of a primary and secondary structure causes some additional work during the implementation and installation. In contrast, the membrane-shell load-bearing behaviour is used for reinforced concrete construction, but it is faced with some technical problems. The free formability of concrete is very good indeed, but the required formwork and its preparation for the generation of free formed concrete structures is a major cost factor. In addition, the high level of reinforcement and the poor corrosion properties of structural steel can increase the thickness of the component and the expenditure of reinforcement work is significantly. Besides the technical aspects, the simulation and the analysis have a high degree of complexity. New approaches and methods are needed likewise, which enables the architect and the structural engineer to optimize the geometry and materiality in an early design phase. Through the use of fibre reinforced polymers, the research group try to implement and explore efficient freeform concrete structures by an ongoing research project. These materials have a high strength and stiffness and permit the engineer to design his own material. In particular, this means that architects and structural engineers have a lot of freedom and do not have to resort to ready-made materials as is usual. By the choice of the material components, the number of layers and especially by the orientations of the fibres, the anisotropic material properties can be controlled. Therefore, engineers have the opportunity to design the component to external effects, such as wind or snow, that the material is used highly efficient. The aim of the intended design principle pursued in the research project is to develop high-precision manufactured, free formed, fibre-based panels, as stay-in-place formwork for concrete freeform structures. Here the plates should be mounted self-supporting at the site without any elaborated substructure and used as formwork for concreting afterwards. After hardening of the concrete, the CFRP elements remain in the component and are used for load transfer, primarily to take the tensile forces. The new type of construction makes it possible to avoid complicated formwork, to guarantee a high level of design quality based on prefabrication and to implement material saving designs. Due to experiments, initial satisfactory findings on the bond behaviour between concrete and carbon could be investigated and implemented in the simulation.