Omikrine Metalssi O.,IFSTTAR |
Ait-Mokhtar A.,University of La Rochelle |
Turcry P.,University of La Rochelle |
Construction and Building Materials | Year: 2012
This paper presents the consequences of the carbonation phenomenon in the case of a mortar with cellulose ether as admixture on its mechanical properties, microstructure and length variations. Carbonation was found to improve mechanical strengths and decrease the global porosity with modifying the pore size distribution. The latter is beneficial regarding durability. However, carbonation also led to an increase of shrinkage, and thus to a probable increase of cracking. Carbonation and shrinkage kinetics could be slowed down by sheltering the material from carbonation during hardening. © 2012 Elsevier Ltd. All rights reserved.
Jouanneau S.,University of Nantes |
Recoules L.,CNRS Laboratory for Analysis and Architecture of Systems |
Durand M.J.,University of Nantes |
Boukabache A.,CNRS Laboratory for Analysis and Architecture of Systems |
And 6 more authors.
Water Research | Year: 2013
The Biochemical Oxygen Demand (BOD) is one of the most widely used criteria for water quality assessment. It provides information about the ready biodegradable fraction of the organic load in water. However, this analytical method is time-consuming (generally 5 days, BOD5), and the results may vary according to the laboratory (20%), primarily due to fluctuations in the microbial diversity of the inoculum used.Work performed during the two last decades has resulted in several technologies that are less time-consuming and more reliable. This review is devoted to the analysis of the technical features of the principal methods described in the literature in order to compare their performances (measuring window, reliability, robustness) and to identify the pros and the cons of each method. © 2013 Elsevier Ltd.
Boulch A.,University Paris Est Creteil |
Houllier S.,University Paris Est Creteil |
Marlet R.,University Paris Est Creteil |
Computer Graphics Forum | Year: 2013
We propose a new approach to automatically semantize complex objects in a 3D scene. For this, we define an expressive formalism combining the power of both attribute grammars and constraint. It offers a practical conceptual interface, which is crucial to write large maintainable specifications. As recursion is inadequate to express large collections of items, we introduce maximal operators, that are essential to reduce the parsing search space. Given a grammar in this formalism and a 3D scene, we show how to automatically compute a shared parse forest of all interpretations - in practice, only a few, thanks to relevant constraints. We evaluate this technique for building model semantization using CAD model examples as well as photogrammetric and simulated LiDAR data. © 2013 The Author(s) Computer Graphics Forum © 2013 The Eurographics Association and John Wiley & Sons Ltd.
News Article | February 21, 2017
In collaboration with the international CITYOPT project, VTT Technical Research Centre of Finland has developed an energy planning tool for experts and an application for consumers. The tools have been piloted in Helsinki, Nice and Vienna, with promising results. Local energy costs were reduced by 15% and carbon dioxide emissions by 30% using the optimal planning feature of the tool for experts. Using the game-like tablet application, almost 80% of the households involved managed to reduce their electricity consumption during peak times. The CITYOPT Planning Tool, which was developed to meet the needs of energy experts and investors, enables optimisation of the energy planning of large-scale urban and regional systems. The tool provides alternative plans with cost and functional evaluations, enabling the minimisation of energy costs and CO2 emissions, for example. It also provides holistic solutions instead of partial optimisation. Over the long-term, the benefits of urban planning are also passed on to the tax payer. The tool has been piloted in Helsinki and Vienna. Optimal planning at the case locations achieved reductions of around 15% in energy costs and 30% in CO2 emissions. The planning tool also markedly reduces the time required for planning. The aim of the CITYOPT Operational Tool for consumers is to reduce the household load during peak-time power consumption and prevent problems with electricity production in advance. The tablet application was piloted in 140 households in Nice during the project. Consumer trials showed that cuts in power consumption can be achieved when end users are sufficiently motivated. Almost 80% of households reduced their electricity consumption when the need to do so arose. The application provides information on household electricity consumption and how it can be reduced. It increases consumers' awareness of energy efficiency and their opportunities to influence their own consumption. The consumer can choose whether to participate in cutting his or her own electricity consumption and how, i.e., which load to shift temporally. For example, during peak loads consumers can lower the lighting power or change their laundry time. Participation is rewarded by allocating points for reducing and moving loads. The consumer can give his or her points to a local charity, with the power company paying the charity accordingly. This creates a direct, small energy saving for the consumer and financial benefits for charitable activities in the community, while electricity producers benefit from a more economical production method when avoiding peak production capacity. Consumers can save around EUR 5 per year, which is fairly small. However, this was anticipated since the aim was to shift power loads during peak-time consumption rather than actually lowering electricity bills. The need to shift consumption was brief, occurring between 6 pm and 8 pm on days during which peak electricity consumption was being reached. CITYOPT project was coordinated by VTT, the project began in February 2014 and ended in January 2017. Its budget was EUR 3.9 million and EU FP7 was the funding agency. VTT, AIT from Austria, CSTB and EDF from France, Experientia from Italy, Helen Oy and the cities of Helsinki and Nice participated in the project. http://www. The CITYOPT planning tool for energy experts and investors: https:/ VTT Technical Research Centre of Finland Ltd is the leading research and technology company in the Nordic countries. We use our research and knowledge to provide expert services for our domestic and international customers and partners, and for both private and public sectors. We use 4,000,000 hours of brainpower a year to develop new technological solutions. VTT in social media: Twitter @VTTFinland, Facebook, LinkedIn, YouTube, Instagram and Periscope.
Courchay J.,IMAGINE |
Pons J.-P.,CSTB |
Monasse P.,IMAGINE |
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010
In this paper, we propose a novel method to simultaneously and accurately estimate the 3D shape and 3D motion of a dynamic scene from multiple-viewpoint calibrated videos. We follow a variational approach in the vein of previous work on stereo reconstruction and scene flow estimation. We adopt a representation of a dynamic scene by an animated mesh, i.e. a polygonal mesh with fixed connectivity whose time-varying vertex positions sample the trajectories of material points. Interestingly, this representation ensures a consistent coding of shape and motion by construction. Our method accurately recovers 3D shape and 3D motion by optimizing the positions of the vertices of the animated mesh. This optimization is driven by an energy function which incorporates multi-view and inter-frame photo-consistency, smoothness of the spatio-temporal surface and of the velocity field. Central to our work is an image-based photo-consistency score which can be efficiently computed and which fully handles projective distortion and partial occlusions. We demonstrate the effectiveness of our method on several challenging real-world dynamic scenes. © Springer-Verlag 2010.
Faure X.,CSTB |
Le Roux N.,CSTB
Building and Environment | Year: 2012
The displacement ventilation process is studied through analytical time dependent tools. The characteristic times, the interface overshot and the steady state height are analysed step by step considering heat transfers within the volume envelope. In a first step, the influence of heat losses is analysed, followed by the thermal mass (heat storage) on the displacement ventilation process. Finally, the coupling of both is considered. The analyses are done using both dimensional and dimensionless approaches in order to keep physical values for the consideration of thermal transfer in a first part and to give global view of the acting forces in a second part. Results show the great influence of both thermal losses and thermal storage on the ventilation processes. The overshot phenomenon is strongly enhanced by the thermal mass while the thermal losses limit the dynamics of the displacement process. Depending on the values of both, their coupling can result to enhancing the interface height overshot or increasing the global time scale process. Anyway, thermal transfers are important to be considered while designing displacement ventilation strategies. © 2011 Elsevier Ltd.
Racher P.,University Blaise Pascal |
Laplanche K.,University Blaise Pascal |
Dhima D.,CSTB |
Bouchair A.,University Blaise Pascal
Engineering Structures | Year: 2010
As timber is a combustible material, fire safety is a significant obstacle for the development of timber usage in buildings. Among the various structural components, the connections are often the weakest elements in a timber construction. In fire as well as in normal conditions, they govern the load-bearing capacity of the structure. However, a lack of knowledge is pointed out for the design of connections in normal conditions and even more in fire conditions. In this paper, a three-dimensional finite element approach is developed to investigate the performance of dowelled timber connections in fire. The 3D mechanical model and the thermo-physical model for each connection component are described. For the mechanical model, the plastic behaviour of the materials is considered using the Von Mises criterion for steel and the Hill criterion for timber. Then a thermal and mechanical validation of the proposed model is achieved by comparison with the experimental results in normal and fire situations. The analysis is then focused on the behaviour of dowelled timber connections in a fire situation. Thus, timber-to-timber and steel-to-timber connections with fasteners of 12 to 20 mm in diameter are studied considering a load in direct tension parallel to the grain. A parametric analysis, based on the numerical model, is done to evaluate the influence of the timber thickness on the reduction of the load-bearing capacity of the connections. This influence is evaluated considering the time of fire resistance to deduct simple design methods. © 2009 Elsevier Ltd. All rights reserved.
Lefort A.,Supelec |
Bourdais R.,Supelec |
Ansanay-Alex G.,CSTB |
Energy and Buildings | Year: 2013
In this paper, a hierarchical control structure based on model predictive control (MPC) is proposed for managing energy in residential houses. The control objective is to minimize the building energy cost while fulfilling various constraints. The optimization problem takes into account the fluctuations of the energy tariff and the available power that can be supplied by the grid market. The structure is composed of two anticipative layers: a scheduling MPC (S-MPC) with a long time horizon, and a piloting MPC (P-MPC) dealing with short time horizon. This two-level MPC structure is explained in details and compared to a centralized control approach. The methodology is assessed on a case study, developed in SIMBAD, a MATLAB toolbox dedicated to building modeling and simulation. This representative case study is used to compare this hierarchical approach with a classical control structure. © 2013 Elsevier B.V.
El-Mazry C.,CSTB |
El-Mazry C.,Arts et Metiers ParisTech |
Ben Hassine M.,Arts et Metiers ParisTech |
Correc O.,CSTB |
Colin X.,Arts et Metiers ParisTech
Polymer Degradation and Stability | Year: 2013
Thermal aging of an additive free PA 6-6 has been elucidated at 90, 100, 120, 140, 150 and 160°C in air-ventiled ovens by Fourier transform infrared spectrophotometry, viscosimetry in molten state and uniaxial tensile testing. Oxidation of methylene groups starts after a considerably shorter induction period but reaches a lower maximal rate than in additive free PE. Cleavage of C-N bonds constitutes the main source of chain scissions. It leads to the formation of aldehyde chain-ends and a catastrophic decrease in molar mass. Embrittlement occurs at a very low conversion ratio of the oxidation process, in particular when the concentration of aldehyde chain-ends reaches a critical value of [PH=O]F ≈ 5.6 10-3 mol l-1, corresponding to a critical value of the number average molar mass of M nF ≈ 17 kg mol-1. At this stage, the entanglement network in the amorphous phase is deeply damaged. A non-empirical kinetic model has been derived from the oxidation mechanistic scheme previously established for PE, but improved by adding elementary reactions specific to polyamides such as the rapid decomposition of unstable hydroxylated amide groups. This model describes satisfyingly the main features of the thermal oxidation kinetics of PA 6-6, but also of other types of aliphatic polyamides studied previously in the literature such as: PA 6, PA 12 and PA 4-6, as long as it is not controlled by oxygen diffusion. At the same time, it confirms the existence of an universal character for the thermal oxidation kinetics of aliphatic polyamides whatever their origin, i.e. their initial molar mass, crystallinity ratio, concentration of impurities, structural irregularities, etc. © 2012 Elsevier Ltd. All rights reserved.
El-Mazry C.,CSTB |
El-Mazry C.,Arts et Metiers ParisTech |
Correc O.,CSTB |
Colin X.,Arts et Metiers ParisTech
Polymer Degradation and Stability | Year: 2012
PA 6-6 hydrolysis at 60, 70, 80 and 90°C in distilled water has been studied by Fourier transform infrared spectroscopy, viscometry in molten state, differential scanning calorimetry and uniaxial tensile testing. The molar mass decreases sharply from the early periods of exposure to reach an equilibrium value of about M nE ≈ 10-11 kg mol -1 almost temperature independent. Hydrolytic chain scissions destroy the entanglement network in the amorphous phase and liberate small macromolecular segments which rearrange locally and initiate a chemicrystallisation. As expected, the embrittlement occurs at a very low conversion of the hydrolysis, in particular when the number average molar mass becomes lower than a critical value of about M nF ≈ 17 kg mol -1, i.e. very close to its initial value. A new kinetic model has been derived from the classical mechanistic scheme of reversible hydrolysis. This model describes satisfyingly all the kinetic characteristics of the reversible hydrolysis of PA 6-6 not controlled by water diffusion: decrease in molar mass, increase in crystallinity ratio and decrease in ultimate elongation, but also of other types of polyamides previously studied, such as PA 11. Moreover, when it is used as an inverse method, this model gives access to the rate constants of hydrolysis and condensation reactions. It is thus an interesting tool for elucidating structure/rate constant relationships in common families of hydrolysable polymers. © 2012 Elsevier Ltd. All rights reserved.