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Saint-Sauveur-en-Rue, France

Kondyli A.,ANKA Consulting Engineers | Soria I.,University of Illinois at Springfield | Duret A.,Center Detudes Techniques Of Lequipement | Elefteriadou L.,University of Florida
Simulation Modelling Practice and Theory

Various microscopic simulation models have been used for studying traffic operations along freeway segments. An important desirable function of these models is their ability to obtain capacity and replicate the breakdown process realistically. The objectives of this paper are to evaluate the capability of a microsimulation model, CORSIM, to replicate the process of breakdown and to perform a sensitivity analysis on driver behavior parameters. The research findings indicate that CORSIM has some strengths and some weaknesses with respect to the breakdown process. Sensitivity analysis shows the different effects of these parameters on the breakdown occurrence and provides recommendations on the application of these parameters to provide a more realistic representation of traffic operations. © 2011 Elsevier B.V. All rights reserved. Source

Imine H.,French Institute of Science and Technology for Transport | Benallegue A.,University of Versailles | Madani T.,University Paris Est Creteil | Srairi S.,Center Detudes Techniques Of Lequipement
IEEE Transactions on Vehicular Technology

In this paper, an original method about heavy-vehicle rollover risk prediction is presented and validated experimentally. It is based on the calculation of the load transfer ratio (LTR), which depends on the estimated vertical forces using high-order sliding-mode (HOSM) observers. Previously, a tractor model is developed. The validation tests were carried out on an instrumented tractor rolling on the road at various speeds and lane-change maneuvers. Many scenarios have been experienced: driving tests in a straight line, a curve, and a zigzag line, and brake tests to emphasize the rollover phenomenon and its prediction to set off an alarm to the driver. In this paper, the vehicle dynamic parameters (masses, inertia, stiffness, etc.) and the static-force infrastructure characteristics (road profile, radius of curvature, longitudinal and lateral slopes, and skid resistance) are measured or calculated before the tests. © 2013 IEEE. Source

Pavoine A.,Center Detudes Techniques Of Lequipement | Brunetaud X.,French National Center for Scientific Research | Divet L.,Institute Franais des science et Technologies des Transports
Cement and Concrete Composites

Delayed Ettringite Formation (DEF) in concrete is likely to lead to swelling and cracking in structures which have undergone early age heating to a temperature of over 65°C. Application of a method that accelerates this process has made it possible to study the impact of cement properties on DEF. For two temperatures reached by the concrete (75°C or 85°C), the study considers a domain defined by the sulphate content [2.6-3.6%], the alkali content [0.5-1%] and the Blaine specific area [3330-4635 cm 2/g] of the cement. The impact of these parameters and the interactions between them on swelling are discussed. Monitoring of the dynamic elastic modulus of the concretes shows that this property may be reduced by DEF, but that it may increase again once the swelling process has ceased, probably due to the gradual filling of voids by ettringite formed under conditions of limited supersaturation. © 2011 Elsevier Ltd. All rights reserved. Source

Heloise C.,CNRS Institute of Earth Sciences | Heloise C.,Center Detudes Techniques Of Lequipement | Heloise C.,ITSAK Institute of Engineering Seismology and Earthquake Engineering | Bard P.-Y.,CNRS Institute of Earth Sciences | Rodriguez-Marek A.,Virginia Polytechnic Institute and State University
Bulletin of Earthquake Engineering

When data is available, the estimation of site effects is usually performed using the "standard spectral ratio" (SSR) technique with respect to an outcropping, reference rock site. This study uses the Japanese KiK-net network, which has more than 600 pairs of surface-downhole stations allowing the computation of empirical borehole transfer functions, consisting of mean spectral ratios of surface over downhole recordings. The borehole transfer function deviates from the SSR in two respects: the reference is located at depth, and the downhole velocity varies from one site to another. These differences bias the estimation of the transfer function with reference to a standard outcrop rock site. The goal of this paper is to develop a simple and robust methodology to correct for such bias. The proposed correction procedure consists of two steps: a depth correction designed to account, in a simplified and physically acceptable way, for the existence at depth of destructive interferences and the absence of free-surface effects in the high-frequency range; and an impedance correction designed to normalize the shear wave velocity at depth. The depth correction involves a simple, frequency-dependent curve to be adapted for each site as a function of the first destructive interference frequency at depth. The impedance normalization combines the use of "generic" rock velocity profiles and a quarter-wavelength approach, resulting in a smooth frequency-dependent amplitude correction. The proposed methodology is applied on a large subset of KiK-net data in view of analysing the correlation between site amplification factors and site parameters in a companion paper. © 2011 Springer Science+Business Media B.V. Source

Idir R.,CNRS Materials and Construction Durability Laboratory | Idir R.,Universite de Sherbrooke | Idir R.,Center Detudes Techniques Of Lequipement | Cyr M.,CNRS Materials and Construction Durability Laboratory | Tagnit-Hamou A.,Universite de Sherbrooke
Materials and Structures/Materiaux et Constructions

This paper deals with the incorporation of glass cullet in cement-based materials. The aim is to help understand the differing behaviours observed depending on the particle size of the glass: the use of fine powders usually improves the concrete properties due to pozzolanic reaction, while coarse aggregates are generally detrimental for concrete due to alkali-silica reaction. It is shown that the lack of swelling of gels resulting from the reaction of glass fines can be partly due to the nature of these gels. The comparative investigation carried out on reaction products resulting from glass grains of various sizes, in the presence of both portlandite Ca(OH)2 and C 3S (tricalcium silicate: 3CaO · SiO2), has shown that glass aggregates produce detrimental gels while glass fines produce gels that help to improve concrete properties. © 2012 RILEM. Source

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