Topic 2 - Hybrid and multiscale design of structures

Theme 2.1 - Ecologically responsible design

This theme is integrated into each of the activities of Topic 2. It is taken into consideration during all stages of a structure’s life: choice of concrete, structural concepts, integration of construction methods, selection of repair materials, planning of deconstruction methods and reuse or recycling of materials (P3 and P4). The confinement of deteriorated or reactive concrete in existing structures using fibre-reinforced concrete (FRC, UHPFC) or fibre-reinforced polymer (FRP) cladding will allow for a better use of natural resources and contribute to the recycling of demolished structures without affecting the quality and safety of certain structures. The use of light prefabricated elements for the accelerated construction of bridges and buildings, especially in urban environments, requires changes in standards and practices that often call for the use of better-performing materials, which over time, leads to a reduction in the environmental impact (P5).

Theme 2.2 - Multiscale design of materials through the optimization of their micromechanical properties

This theme is at the borderline between Topic 1 and Topic 2. The optimization of macroscopic structural properties and durability in new cementitious composites is carried out using a multiscale approach that establishes a functional link between some parameters of their microstructure and macroscopic performances (compressive and tensile strength, elastic modulus and creep). Decoding of the microstructure of cementitious composites is key to building an optimization approach. The new techniques developed pair nanomechanics and spectroscopy, and allow detection of microstructural phases and the coupling of micromechanical properties. These micrometric-scale techniques help characterize creep itself and the elastic properties of concrete. This design approach will allow to optimize micromechanical characteristics in accordance with the expected macroscopic performance of the concrete elements (P4).

Theme 2.3 - Development of design tools

The penetration of harmful agents in concrete, the initiation and opening of cracks, and the interaction between repair materials and original materials are but a few examples of the essential data required in an ecologically responsible design context (P1, P3 and P4). Digital tools are developed and validated experimentally to enable their forecasting in the complex exercise of concrete lifespan assessment, based on their chemical composition and anticipated conditions of use in order to make choices related to the durability characteristics required. Other tools help predict the mechanical and structural behaviour of structures in service and at the end of useful life, by integrating interactions between the different materials and components at different structural scales. To ensure reliability, the non-linear mechanical and thermal behaviours of the various components must be considered.

Theme 2.4 - Development of innovative structural elements

The construction and repair of concrete structures increasingly make use of structural elements whose mechanical, geometric, aesthetic and durability characteristics must meet very specific performance objectives. FRC and UHPFC structural elements offer innovative solutions to better satisfy weight, complex geometry, on-site assembly and architectural constraints (P4). The research seeks to use optimized FRC and UHPFC (workability, ductility, volume stability and affordable cost) to produce innovative structural elements. A hybrid system currently under study consists of reinforced concrete placed in FRP tubes used as permanent moulds, and whose confinement role makes it possible to anticipate a structural capacity and ductility three times greater than those of reinforced concrete elements (P5). Hybrid flooring systems incorporating light and ductile concrete and wood are also being studied.

Theme 2.5 - Prefabricated and modular construction

This theme deals with the development of prefabricated modular structures to minimize the impact of construction work on users and residents, thus ensuring superior manufacturing quality and reducing material consumption (P1). The upstream research aims to improve our understanding of the failure mechanisms inherent to prefabricated and modular structures, where connections are highly stessed (concentration of stresses requiring a large ductility reserve). One of the substantive objectives is the increased use of the innovative structural elements described in Theme 2.4. Activities include the experimental characterization of various real-size structural elements used in buildings, engineered structures and other state-of-the-art construction projects, by integrating very advanced characteristics (e.g., electro-mechanical services) requiring a resolutely multidisciplinary design approach (architecture, civil, mechanical, and electrical engineering and BIM) (P1 and P4).