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Champs-sur-Marne, France

Schlosser F.,ENPC | Servant C.,Eiffage Travaux Publics | Guilloux A.,TERRASOL | Bergere A.,TERRASOL
Journal of Rock Mechanics and Geotechnical Engineering | Year: 2013

The Millau viaduct over the Tarn River is an exceptional bridge considering the height under the deck and the 2.5. km total length. Each of the seven high piers is founded on a thick raft setting on four large piles of 5. m in diameter and 10-15. m deep. The ground schematically consists of limestone in the north and of marls in the south. As the bridge is very sensitive to foundation settlements, the concessionary company decided to use the observational method for controlling the displacements and if necessary stabilize the foundations. The measurements show that the movements have remained small and admissible, particularly in terms of the rotations. The settlements have not occurred continuously under the load, but by steps. © 2013 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Source


Chevalier G.,ENPC | Le Ny J.,Ecole Polytechnique de Montreal | Malhame R.,Ecole Polytechnique de Montreal
Proceedings of the American Control Conference | Year: 2015

Studies of traffic dynamics rely either on macro-scopic models considering the traffic as a fluid, or on micro-scopic models of drivers' behavior. The connection between the microscopic and macroscopic scales is often done via empirical relationships such as the fundamental diagram for macroscopic models, relating traffic flow or average velocity and traffic density. In this paper, we consider a microscopic model consisting of a large number of rational, utility-maximizing drivers interacting on a single road. We then use the theory of Mean Field Games (MFG) to deduce a macroscopic model of traffic density emerging from these interactions. We show how to determine a microscopic utility function for the drivers compatible with standard empirical macroscopic fundamental diagrams. In addition to connecting the microscopic and macroscopic models analytically rather than empirically, our approach can offer additional flexibility to model drivers at the macroscopic level, using a Hamilton-Jacobi-Bellman equation coupled with the standard conservation law for the vehicles. © 2015 American Automatic Control Council. Source


Cui K.,Southwest Jiaotong University | Defossez P.,French National Institute for Agricultural Research | Cui Y.-J.,ENPC | Richard G.,French National Institute for Agricultural Research
Geomechanics and Geotechnics: From Micro to Macro - Proceedings of the International Symposium on Geomechanics and Geotechnics: From Micro to Macro, IS-Shanghai 2010 | Year: 2011

Compressibility is closely related to the stability of geotechnical engineering structures made of compacted soils. Most analysis neglects the variation of suction during the compaction. A standard oedometer cell equipped with a tensiometer was used to measure soil suction continuously during the application of different vertical stresses. Measurements were carried out on remolded soil samples obtained by compacting a loamy soil sieved 2 mm and 0.4 mm at an initial dry density of 1.1 g cm -3 and at different initial water suctions. The results showed that the suction remained almost constant until a vertical stress threshold value beyond which the suction decreased as the stress increased. Furthermore, the results obtained highlighted the effect of soil structure on the stress threshold. Variations in soil suction were interpreted in term of processes at pore scale by comparing the evolution of pore-size distribution, measured by mercury intrusion, and the expected distribution of water in the pores. © 2011 Taylor & Francis Group. Source


Leger R.,ONERA | Peyret C.,ONERA | Piperno S.,ENPC
16th AIAA/CEAS Aeroacoustics Conference (31st AIAA Aeroacoustics Conference) | Year: 2010

We focus on the study of a coupling algorithm applied to direct acoustic waves simulation. The idea is to introduce a partition of the computational domain, and to be able to use meshing techniques and numerical methods of different natures in order to meet the local requirements of the computation. Here, we solve the Linearized Euler Equations and couple a Discontinuous Galerkin method (DGM) running on an unstructured mesh and a Finite Difference method (FDM), running on a Cartesian grid. The aim is to take into account complex geometries by running a DGM and run a FDM away from the obstacles to reduce computational cost. In this paper, we present a DG/FD coupling algorithm and discuss some preliminary validation elements. © 2010 by Raphaël Léger. Source


de Palma A.,Ecole Normale Superieure de Cachan | de Palma A.,Ecole Polytechnique - Palaiseau | Picard N.,Ecole Polytechnique - Palaiseau | Picard N.,Cergy-Pontoise University | Andrieu L.,ENPC
Networks and Spatial Economics | Year: 2012

We discuss how the standard Cost-Benefit Analysis should be modified in order to take risk (and uncertainty) into account. We propose different approaches used in finance (Value at Risk, Conditional Value at Risk, Downside Risk Measures, and Efficiency Ratio) as useful tools to model the impact of risk in project evaluation. After introducing the concepts, we show how they could be used in CBA and provide some simple examples to illustrate how such concepts can be applied to evaluate the desirability of a new project infrastructure. © 2009 Springer Science+Business Media, LLC. Source

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