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Wang L.,Ecole Polytechnique - Palaiseau | Bornert M.,University Paris Est Creteil | Heripre E.,Ecole Polytechnique - Palaiseau | Chanchole S.,Ecole Polytechnique - Palaiseau | And 2 more authors.
Journal of Geophysical Research B: Solid Earth | Year: 2015

The mechanical behavior of mudstones strongly depends on humidity. In this paper, we present some microstructural insights into this phenomenon gained from a microscale investigation using a novel experimental method. The experimental method consists of combined hydric and mechanical loading tests in environmental scanning electron microscopy, as well as full-field strain measurement by digital image correlation techniques. The sample is subjected to a stepwise wetting (21%, 80%, and 99% relative humidity); for each equilibrium moisture state, a uniaxial compression test is performed. The microscale observation reveals that humidity-induced changes in the mechanical behavior of mudstones are controlled by the deformation and microcracking upon wetting. With increasing relative humidity, expansion of pores causes the clay matrix to be softer. In addition, because of the reduction in shear modulus and the lessening of capillary effect, shear bands are prone to appear at a high humidity state. The microcracking upon wetting, which results in predamage of the material, also affects the mechanical behavior. Finally, the sample with more moisture exhibits a more ductile behavior that involves more pronounced microcracking at failure. ©2015. American Geophysical Union. All Rights Reserved. Source

Wang L.L.,Ecole Polytechnique - Palaiseau | Bornert M.,University Paris Est Creteil | Yang D.S.,Chinese Academy of Sciences | Heripre E.,Ecole Polytechnique - Palaiseau | And 4 more authors.
Engineering Geology | Year: 2015

Argillaceous rocks are chosen as possible host rocks for underground radioactive nuclear waste disposal. These rocks exhibit complex coupled thermo-hydro-chemo-mechanical behavior, the description of which would strongly benefit from an improved experimental insight on micro-scale. In this work we present some recent observations of the evolution of these rocks upon swelling on the scale of their composite microstructure, essentially made of a clay matrix with embedded grains of calcite and quartz with sizes ranging from a few to several hundreds of micrometers. The micro-scale experimental investigation was based on the combination of high definition and high resolution imaging in an environmental scanning electron microscope (ESEM) and digital image correlation techniques. Samples were held at a constant temperature of 2. °C while the vapor pressure in the ESEM chamber was varied from a few to several hundreds of Pascals, generating a relative humidity (RH) ranging from about 10% up to 99%. Results on micro-scale showed strongly heterogeneous deformation fields, which result from complex hydromechanical interactions between different components of argillaceous rocks. The swelling of argillaceous rocks is moderate at low RH but becomes significant at high RH. The observations demonstrated that the nonlinearity is related not only to the micro-cracking upon wetting, but also to the nonlinear swelling of the clay matrix itself that is governed by different mechanisms. © 2015 Elsevier B.V.. Source

Continuous shear connection, using a cut steel strip, is an upcoming solution for composite beams. With the activation of friction on the sides of the steel strip this method has already been used to design and build large durable bridges during the sixties. However direct shear transmission into the steel strip though teeth of the cut is also possible and has been scrutinized with the support of the European Research Fund for Coal and Steel. It is characterized by a high initial stiffness, bearing capacity and ductility. It allows new and economic construction methods, as the PreCoBeams (Prefabricated Composite Beam used as formwork). PreCoBeams are for instance composite beams associating steel T-sections acting as tension member with a concrete top chord acting as compression member. Steel parts are generally obtained from rolled steel profiles that are longitudinally cut in two identical T-sections. The cut is performed with a special shape to allow the shear longitudinal transmission between steel and reinforced concrete. In general, prefabricated, composite, longitudinal PreCoBeam bridge elements are produced in factory. They consist of at least one steel T-section associated to a precast first phase concrete flange. Second phase concrete layer is then completed in-situ after erection of the bridge elements on abutments. These PreCoBeam bridges are very economic in design and construction, though the main market drawback for PreCoBeams is the missing design rules for the shear connection. This paper introduces the static and fatigue design of continuous steel plate shear connections used for PreCoBeams derived from the recent research activities. The CL shape of the cutting has been tested in fatigue, ultimate and service limit states and validated in the scope of a bridge application. This concept aims at developing a competitive solution for small span bridges. The various solutions realized in the last years in many European countries, some of them presented in the paper, show clearly its interest. © 2013 The Authors. Published by Elsevier Ltd. Source

Hamet J.-F.,INRETS | Besnard F.,British Petroleum | Doisy S.,LRPC | Lelong J.,INRETS | Le Duc E.,Setra
Applied Acoustics | Year: 2010

Traffic noise prediction models in France are based on vehicle noise emission values defined by the French Guide du Bruit des Transports Terrestres (Noise Guide for Ground Transport-Noise levels prediction). These emission values are suited for models addressing the noise assessments of road infrastructures and the dimensioning of acoustic protections, needing traffic noise estimations in terms of ŁAeq over a long period of time (an hour or more). The values, obtained from measurements collected in the 70s, are updated in the publication of a new guide (Methodological Guide, Vehicle noise emissions, to be published), which addresses the road surface influence on tyre/road noise. The emission values are now expressed through the contributions of a power unit component, function of traffic speed, traffic flow type and road declivity, and of a rolling noise component, function of traffic speed and road pavement. The paper outlines the procedures followed to determine the components, gives their numerical values, and illustrates some vehicle noise emissions. © 2010 Elsevier Ltd. All rights reserved. Source

Thiery M.,University Paris Est Creteil | Cremona C.,Setra | Baroghel-Bouny V.,University Paris Est Creteil
European Journal of Environmental and Civil Engineering | Year: 2012

Deterministic approaches for the prediction of the carbonation penetration have limitations related to the high variability of the input data. This paper deals with two carbonation models which are developed in the framework of a probabilistic approach. The random input data are presented, i.e. materials, environment and engineering design properties. The evaluation of the time-dependent probability of carbonation-induced reinforcement corrosion is assessed by calculating the reliability index for three studied concretes. This probabilistic approach provides a framework for a sensitivity analysis which enables one to identify the most influencing model parameters which have to be determined carefully in order to improve the accuracy of the prediction and to determine the parameters whose variability should be reduced to enhance the durability. Furthermore, a probabilistic approach provides a tool to design the thickness of the concrete cover in order to avoid oversizing. © 2012 Taylor & Francis. Source

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