Durability | EPFL Graph Search

Durability is the ability of a physical product to remain functional, without requiring excessive maintenance or repair, when faced with the challenges of normal operation over its design lifetime. There are several measures of durability in use, including years of life, hours of use, and number of operational cycles. In economics, goods with a long usable life are referred to as durable goods. Requirements for product durability Product durability is predicated by good repairability and regenerability in conjunction with maintenance. Every durable product must be capable of adapting to technical, technological and design developments. This must be accompanied by a willingness on the part of consumers to forgo having the "very latest" version of a product. In the United Kingdom, durability as a characteristic relating to the quality of goods that can be demanded by consumers was not clearly established until an amendment of the Sale of Goods Act

Combined Ramp and Squeeze at the Large Hadron Collider

Nick Ryckx

In the first two years of operation of the CERN Large Hadron Collider (LHC), the betatron squeeze has been carried out at constant flat top energy of 3.5 TeV. Squeeze setting functions are separated from the energy ramp functions. This ensured a maximum flexibility during commissioning because stopping at all intermediate optics for detailed measurements was possible. In order to then improve the efficiency of the operational cycle, combining the ramp and squeeze has been considered. In this paper, the various possibilities for this scheme are reviewed, and proposals of optimized operational cycles with combined ramp and squeeze are presented for different energies. Results of beam tests are also discussed.

2012

Simulation des phénomènes de dégradation d'éléments de construction

Peter Zurbrügg

Builders have always been concerned about the durability of construction materials and building components. Nowadays, powerful information technology tools offer an opportunity to approach the complexity of aging phenomena in an innovative way. This thesis presents a method and a simulation model designed to predict the aging of multi-layer building components. Integrated into a software tool, they take into account the nature and intensity of the external agents acting on a component. The tool creates possibilities for a variety of applications : it can guide users towards the most appropriate and durable construction systems, it can be helpful in decision making for building maintenance and it can provide service-life information for life-cycle analysis (LCA). The work is based on research undertaken between 1990 and 1997 by the Expert Service from the Construction and Conservation Laboratory (LCC) at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in collaboration with the ARIA-laboratory of the Ecole Nationale Supérieure d'Architecture de Lyon (UMR CNRS n°694 MAP, Hervé Lequay) for the development of the Assistance to Maintenance of Buildings tool (AMB). The goal of the present work was to continue and extend the previous investigations. In a first step, the tool has been analysed and recreated within the Delphi development environment. New parameter recorder modules and graphical analysing modules have been added for better simulation monitoring and visualisation of chain reactions due to degradation processes. The model has also been adapted to allow stochastic simulation with the Monte-Carlo Method. This part of the research permits bringing out the structure of the simulation method's various aspects and concepts and working out its detailed description. In the report, global aspects of the prediction method are presented first. Basic concepts and principles, such as stress actions, material performance and element functions, are described. In a second part, the design of the computer model is presented. The aim is to show how the general concepts of the method can find an application. Various stress agents and specific material performances that participate in the aging process and lead to a decrease in performance are highlighted. Aging is simulated by the interaction between the materials and agents over time. Definitions of the failure criteria for a given building component are made by identification of its functions and assigning performance limits values. Two chapters are dedicated to the detailed description of the different stress agents and performances used in the model. These are followed by a selection of case studies that shows the working of the simulation and illustrates the various types of results that can be obtained. The conclusions reiterate that the prediction of construction material aging is a wide and complex subject. To be able to make not only qualitative but also quantitative durability predictions, further research must be undertaken in different domains. This is necessary in order to collect existing knowledge and to obtain missing information. As the presented method and model can easily integrate new data as it becomes available, they could play the role of a development platform for future investigations. This would allow a progressive increase in the reliability of the predictions.

EPFL2010

Thermal and structural performance of a new fiber-reinforced polymer thermal break for energy-efficient constructions

Kyriaki Goulouti

The thermal bridges constitute critical regions in building envelopes and they are created due to the interruption of the insulation layer. One of the many structural thermal bridges in building envelopes is created in balcony junctions because of the required structural continuity of the concrete slab. The detrimental effects of such thermal bridges are minimized, by using thermal breaks that interrupt the heat flow towards the external environment by adding an intermediate insulation layer between the internal floor and the balcony slab. For the majority of these thermal breaks, the load transfer from the balconyâs cantilever to the main structure occurs through stainless steel bars, which penetrate the insulation layer and still have a high thermal conductivity. The current research proposes a new thermal break composed of fiber-reinforced polymer composite materials (FRP) that have much better thermal properties than the conventional materials and investigates its short- and long-term structural and thermal behavior. The tensile force from the cantilever moment is transmitted by an aramid-FRP (ARFP) loop, whose thermal conductivity is about 170 times smaller than that of stainless steel. The compression component of the moment is transferred by a short glass-FRP (GFRP) element while the shear compression diagonal is transmitted by a FRP-PU hexagonal foam sandwich. The insulation layer is composed of a thin layer of aerogel granulate. All the components are assembled in a polymer box. The thermal performance of the above-mentioned thermal break was validated by estimating its impact on the energy balance of a traditional building, using three different building envelopes (a MINERGIE envelope, a MINERGIE-P envelope and an optimum envelope). Furthermore, 3d finite element steady-state thermal simulations were performed in order to define the true losses through the optimized thermal break. Finally, the thermal behavior of the thermal break was compared with that of traditional thermal breaks. The structural validation of the FRP thermal break included the mechanical characterization of the components through static, long-term and durability experiments. The static experiments of the components comprised tensile experiments (AFRP loop) and compression experiments (FRP-PU hexagonal foam sandwich and GFRP bar). The long-term behavior was evaluated through tensile and compression creep experiments, while its simulation and prediction were achieved by applying traditional creep methods and two new proposed models that were able to predict the secondary creep stage (Gradient regression and Gradient regression with NHPP). The durability was evaluated by their immersion in alkaline environment, simulating that of the concrete. Finally, the total behavior of the balcony junction was examined through full scale beam experiments that led to the analytical modelling of the system.

EPFL2016