Étude d'impact | EPFL Graph Search

Une étude d'impact est une étude technique qui vise à apprécier les conséquences de toutes natures, notamment environnementales, d'un projet d'aménagement pour tenter d'en limiter, atténuer ou compenser les effets négatifs. Étude d'impacts environnementaux Origine et description La prise de conscience, dans les années 1970, de la nécessité de limiter les dommages à la nature s’est concrétisée par des lois obligeant à réduire les nuisances et pollutions, et à atténuer les impacts des grands projets (ou de projets dépassant un certain coût). Longtemps elles n'ont été obligatoires pour les grands projets qu'au-dessus de certains seuils financiers (sans rapports avec les effets environnementaux du projet). Une directive européenne, traduite en France dans la loi Grenelle 2 qui a finalement modifié le code de l'environnement en ajoutant que l’étude d’impact doit porter sur le programme complet de travaux, même si les travaux sont échelonnés dans le temps, et non p

Vague de surf en bassin

Cédric Maxime Egolf

A design of a wave pool for surfing is defined in this work. The geometry is designed in order to optimize the relatively small area available for the project. The bathymetry is suited to the different levels of surfers. A wave generation system composed of aligned plungers is selected in view of minimizing energy consumption and not infringing the patents registered. A 3D model on the CFD software Flow-3D is produced in accordance with the theory to confirm the results obtained. A lateral energy dispersion effect is observed which leads to a non-uniform generated wave height. An estimate of the energy efficiency and cost per wave is calculated, and a study of the main environmental impacts is made.

2020

Optimum design of low environmental impact structures through component reuse

Jan Friedrich Georg Brütting

Load-bearing systems (structures) in buildings and infrastructure contribute to a significant share of adverse environmental impacts (EI) because of resource- and energy-intensive fabrication. A currently overlooked circular economy strategy to reduce EI is to reuse structural components over multiple service cycles, which avoids resource use, energy for reprocessing, and waste. To apply reuse, the design process is fundamentally different to conventional practice: employing reused elements involves solving an inverse process whereby the structure layout (topology and geometry) is a result of available element characteristics (cross-sections and lengths). This thesis proposes a new computational workflow to enable design through reuse in structural engineering. Discrete structural optimization techniques are formulated to design reticular structures (trusses and frames) that make best use of a stock of reclaimed elements (linear bars and beams). The objective is the minimization of EI through optimizing stock element assignment and structure topology subject to ultimate and serviceability limit states. The structure EI is quantified through Life Cycle Assessment (LCA) which includes process impacts for building deconstruction, reconditioning, and transport of reclaimed elements. The design process is formulated as a Mixed-Integer Linear Programming problem which produces global optima, and thus it allows rigorous benchmarking between solutions obtained by varying stock compositions and LCA parameters. In addition, geometry optimization is carried out in sequence with assignment optimization to improve further the structure performance and to reduce cut-off waste. The proposed method is applied to typical engineering structures including roof trusses and multi-story building frames subject to statistically simulated and realistic stocks inventoried from deconstructed buildings. Results show that solutions made from reused steel elements have an up to 60% lower EI compared to minimum-weight solutions made of recycled steel elements. An LCA parametric study shows that long transport distances for reclaimed elements are only marginally important, whereas machine operation during deconstruction has a significant influence on EI. This study concludes that a combination of reused and new elements leads to structures with the least EI. To further extend the application range of component reuse, another method is formulated to synthesize a kit of parts comprising linear bars and spherical joints that can be assembled to form non-modular structures of diverse layouts. Multiple structure geometries are optimized simultaneously with the kit-of-parts composition (number of elements, dimensions, cross-sections). The method is implemented as an interactive design and fabrication workflow which has been successfully applied to build three pavilion-scale prototypes. Results show that reusability of the same set of components for multiple structures requires only half the components compared to one-off construction. In summary, this thesis lays out the foundation for optimum design of structures through component reuse and it provides new benchmarks of attainable EI reductions compared to structures made of new components. The significant EI reduction obtained through applying the proposed workflow fosters a broader implementation of reuse strategies in research and practice.

EPFL2020

Component reuse in structural design: emerging practices and tools for the circular economy

Jan Friedrich Georg Brütting, Corentin Jean Dominique Fivet, Jonas Warmuth

Structural engineers play an increasing role in ensuring the transition towards a more sustainable construction sector: a) they are responsible for the design of the most resource- and energy-intensive part of buildings and infrastructure, and b) they regularly interact with architects, contractors, and clients, and hence are full stakeholders in the overall decision process. Traditionally, structural engineers follow two paths to reduce structure environmental impacts: 1) minimizing the volume of material, and 2) adopting low impact (e.g. low carbon) materials. A third strategy that has recently re-emerged in practice and research is the reuse of structural components over multiple service cycles, which allows drastically reducing raw material use, reprocessing energy, and waste. Therefore, employing reuse strategies in structural design has considerable potential to reduce structure environmental impacts further. Although reuse is not new, systematic adoption in practice implies an important paradigm shift: rather than manufacturing components after the structural system has been designed, the system must be synthesized from a stock of available components. The first part of our contribution provides an overview of historic and contemporary structures that efficiently reuse structural components. It also highlights the influence of component reuse on the structural design process. The second part presents a new computational tool for the conceptual design of structures from a stock of reclaimed elements. The tool combines Combinatorial Equilibrium Modelling, graphic statics, efficient Best-Fit heuristics, and Life Cycle Assessment to explore different design options in a user-interactive way and with almost real-time feedback. The method applicability is demonstrated through a realistic case study for the design of a complex 3D spatial structure made of reclaimed structural elements originating from deconstructed buildings in Switzerland. Results show that structures made of reused elements have a significantly lower environmental impact than solutions made of new material only. Link to the video: https://youtu.be/VCyD1yqXH8w

fib2021