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Clermont-Ferrand, France

Rey G.,University Blaise Pascal | Clair D.,University Blaise Pascal | Fogli M.,University Blaise Pascal | Bernardin F.,CETE de Lyon
Mechanical Systems and Signal Processing | Year: 2011

The work presented here aims to develop a warning device to prevent roadway departure while cornering. Given the random variability arising from the driver, the vehicle and the infrastructure at the entrance of the curve, a probabilistic strategy is adopted to assess the roadway departure risk. Random variables and processes are introduced in a specifically developed vehicle dynamics model. The driver's behaviours are deduced from real traffic measurements. Structural reliability methods are employed to compute a roadway departure risk index, used to take the decision of an alarm triggering. Particular care is brought to the reduction of the computational cost. Refinements made on the standard reliability methods to handle with the model non-linearities and the stochastic dimension are presented. © 2010 Elsevier Ltd.

Ovalle C.,Ecole Centrale Nantes | Ovalle C.,University of Santiago de Chile | Frossard E.,Tractebel Engineering | Dano C.,Ecole Centrale Nantes | And 3 more authors.
Acta Mechanica | Year: 2014

Testing the mechanical response of coarse granular materials requires very large and expensive laboratory equipments. During the 1960s, pioneering experimental programs were carried out on several rockfill dam materials, and those results are still a reference for engineers and researchers. However, only few experimental works have been reported to this day, and due to the scarcity of empirical data, the role of the size effect caused by grain crushing is not well known. To improve understanding of this rarely studied issue and the influence of individual particle strength, this paper analyzes the size effect on rock aggregate crushing strength and its connection with the shear envelope of rockfills. The suitability of the 4-parameter Weibull equation to describe size effects on the crushing strength reported in the literature is discussed. Furthermore, a Weibull statistical analysis was carried out for a wide number of experimental results on rock aggregates, where it has been observed that strength decreases with particle size. In parallel, the results of large triaxial tests on homothetic scaled rockfill samples of 250 and 1,000 mm in diameter reveal that the coarser the material, the higher the amount of grain breakage and the lower the shear strength. The impact of size effects obtained from the experiments is analyzed and discussed in terms of the factor of safety of rockfill slope stability. Furthermore, the results are compared with the only existing theoretical method that links the rock aggregate with the strength of the granular assembly. Good agreement between the empirical results and this theoretical method has been confirmed. © 2014 Springer-Verlag Wien.

Belloche S.,CETE de Lyon
19th Intelligent Transport Systems World Congress, ITS 2012 | Year: 2012

Speed control allows a road operator to adapt in real-time the speed limit to the traffic conditions encountered by road users. However, the impacts of variable speed limits depend mainly on the network characteristics and therefore the deployment of this measure is not always relevant to tackle with congestion. On the Lorrain corridor -a motorway corridor in Eastern France -, congestion often occurs on three specific sections and the most appropriate solution seemed to be the deployment of variable speed limits. However, it was not possible to quantify the impacts of this deployment and to know whether this solution was really effective or not. So, it has then been decided to assess the impacts of this solution before deploying the measure on the three sections, and, despite the fact that it has not yet been done so at least in France, the use of simulation appeared to be the best tool to do so. Consequently, this paper aims at describing the chosen methodology, the problems it has raised, the results of this ex-ante evaluation and the decision that has been taken about the deployment of variable speed limits on these sections.

In addition to its harmful economical and social effects, road traffic congestion is a key contributor of emissions of CO 2 and local pollutants. Many traffic management policies could be implemented to tackle it. However, the impacts of those strategies on air quality and greenhouse effect are poorly predicted by classical assessment procedures. Indeed, current assessment tools are based on aggregated traffic data, which fail to capture the dynamic effects of traffic management policies on traffic flow. This article presents an estimation tool capable of measuring all the effects of traffic management policies. It is based on a commonly used dynamic traffic flow model (AIMSUN) combined with different emission models, in order to identify modelling features leading or not to differences in results. Different models combination have been applied and compared for two traffic regulation strategies: a HOV lane dedicated only to buses and taxis created on the leftmost lane of A1 between Charles de Gaulle airport and Paris, and a reduction of speed limits on a section of motorway A86 in the northwest of Paris. Substantial differences in predictions of different emission models are highlighted. They cannot be entirely explained by differences in emission laws. Other insights with regard to traffic representation and emission models' inputs are also investigated to explain them. © 2012 INRETS et Springer-Verlag France.

Guyot G.,CETE de Lyon | Carrie F.R.,ICEE
WIT Transactions on Information and Communication Technologies | Year: 2012

Following the AZF chemical accident (Toulouse, 2001, 30 dead), a French law was adopted in 2003 that can compel public and private building owners to implement construction work on their buildings to protect occupants against specific accidents. To face the risk of a toxic gas cloud, they may be obliged to adopt a shelter-in-place strategy which mainly consists of identifying a shelter in the building and remaining in this room until the toxic cloud has finally been swept off. In addition to seeking refuge in an airtight room, this strategy called "passive shelter-in-place" also includes closing all external openings and turning off all mechanical ventilation systems and air vents. In order to prove that shelter's air-tightness is sufficient and that the occupants will not be exposed to irreversible effects, simulations are required using for instance the modeling tool named CONFINE. Originally developed by CETE de Lyon, this software is a pressure code able to model the infiltration of a pollutant inside a 3-zone building (shelter, attic and rest of building). This paper aims at giving an overview of CONFINE (governing equations, modelling hypotheses,) and will illustrate its application with examples of shelter-in-place strategy for residential and public buildings. © 2012 WIT Press.

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