Les Ponts-de-Cé, France
Les Ponts-de-Cé, France

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Attard G.,National School of Public Civil Engineering | Rossier Y.,Grenoble Institute of Technology | Eisenlohr L.,Cerema
Journal of Hydrology | Year: 2016

In this paper, underground structures are shown to have a major influence on the groundwater mean age distribution described as a dispersive piston effect. Urban underground development does not occur without impacts on subsoil resources. In particular, groundwater resources can be vulnerable and generate disturbances when this space is exploited. Groundwater age spatial distribution data are fundamental for resource management as it can provide operational sustainability indicators. However, the application of groundwater age modeling is neglected regarding the potential effect of underground structures in urban areas. A three dimensional modeling approach was conducted to quantify the impact of two underground structures: (1) an impervious structure and (2) a draining structure. Both structures are shown to cause significant mixing processes occurring between shallow and deeper aquifers. The design technique used for draining structures is shown to have the greatest impact, generating a decrease in mean age of more than 80% under the structure. Groundwater age modeling is shown to be relevant for highlighting the role played by underground structures in advective-dispersive flows in urban areas. © 2016 Elsevier B.V.

Deliniere R.,CEREMA | Aubert J.E.,CNRS Materials and Construction Durability Laboratory | Rojat F.,CEREMA | Gasc-Barbier M.,CEREMA
Building and Environment | Year: 2014

The use of clay plasters with or without plant fibers (straw, hemp or other) inside buildings is currently showing considerable growth in many countries. Despite this development, there are very few data in the literature on the characteristics of clay plasters. This paper deals with the characterization of five ready-mixed clay plasters from French brickworks using the recent German standard. The work essentially consisted in measuring the flow of fresh clay plasters and their characteristics after hardening (shrinkage, and compressive, flexural and adhesive strength). The characterization of the samples showed that the granular characteristics were practically the same and that the main difference concerned the nature of the clayey minerals they contained: four samples were essentially composed of montmorillonite, chlorite and illite whereas one was only composed of kaolinite. Despite this difference, the flow of fresh clay plasters and their characteristics after hardening (shrinkage, compressive and flexural strength) were very similar and were comparable to the values given by the standard. However, the measurement of the adhesive strength led to two significant problems: the dispersion of the values was very high and the results were markedly different from the values given by the standard. For these reasons, it seems necessary to complete and adapt the procedure for measuring adhesive strength and it could be interesting to develop new tests for the measurement of this important characteristic, either in the laboratory or on building sites. © 2014 Elsevier Ltd.

Berger J.,Pontifical Catholic University of Parana | Mendes N.,Pontifical Catholic University of Parana | Guernouti S.,Cerema | Woloszyn M.,CNRS Laboratory of Design Optimisation and Environmental Engineering | Chinesta F.,École Centrale Nantes
Archives of Computational Methods in Engineering | Year: 2016

This paper presents a review of the use of model reduction techniques for building physics applications. The use of separated representations, the so called Proper Generalised Decomposition (PGD), is particularly investigated. This technique can be applied for efficient building physics modelling at different levels: the wall and multizone models, the whole-building (coupled envelope and air volumes) simulation and their practical applications. The PGD can be formulated as a space-time representation to provide fast and accurate solutions of 2- and 3-dimensional problems at the wall or the whole-building level. Furthermore, the PGD solution allows to treat efficiently parametric problems of practical building applications. © 2016 CIMNE, Barcelona, Spain

Regnier J.,CEREMA | Cadet H.,Pierre Mendès-France University | Bard P.-Y.,ISTerre
Bulletin of the Seismological Society of America | Year: 2016

We present an extensive analysis of the quantitative impact of the nonlinear soil behavior on site response at 174 sites of the Japanese Kiban-Kyoshin (KiK-net) network. The nonlinear to linear site-response ratio (RSRNL − L) is calculated by comparing the surface/downhole Fourier spectral ratio for strong events and for weak events. Three thresholds of surface peak ground acceleration (PGA) are tested to characterize the strong events: 100, 200, and 300 cm/s2, whereas weak events correspond to surface PGA in the 0:1-25 cm/s2 range. This ratio exhibits a typical shape; with a low-frequency part above 1 and a high-frequency part generally below 1, separated by a transition zone around a site-dependent frequency labeled fNL (characterized by RSRNL − L = 1). The average maximum amplitudes of RSRNL − L are 1.4, 1.5, and 1.6, and the minimums are 0.6, 0.5, and 0.5 for PGA thresholds 100, 200, and 300 cm/s2, respectively, showing that nonlinear soil behavior results in significant site-response modifications even for moderate PGA values of 100 cm/s2. The fNL value exhibits a satisfactory correlation with site classifications based on either VS30 (travel-time averaged shear-wave velocity over the top 30 m) or f0 (site fundamental frequency): fNL decreases when either VS30 or f0 decreases. In addition, the amount of the low-frequency amplification increase depends on VS30 and reaches a maximum of 1.6 for high VS30 soil classes associated with shallow thin soft-soil layer underlain by stiff substratum. The average high-frequency decrease is about 0.5 for all soil classes defined from either VS30 or f0; for a few sites, however, this decrease is replaced by an increase as reported in previous studies, in relation with water contents and pore-pressure issues. The increase of amplification below fNL is found to be a quasi-systematic consequence of nonlinear soil behavior, which should be emphasized, because it can reach up to 1.6 for high VS30 sites. © 2016, Seismological Society of America. All rights reserverd.

Arena A.,University of Rome La Sapienza | Pacitti A.,CEREMA | Lacarbonara W.,University of Rome La Sapienza
International Journal of Solids and Structures | Year: 2016

A geometrically exact mechanical formulation is proposed to describe three-dimensional motions of flexible cables without any restriction on the amplitude of such motions. The nonlinear equations of motion are formulated via an updated Lagrangian formulation taking the prestressed catenary equilibrium under gravity as the start configuration. By employing a single space coordinate parametrization, the kinematics feature finite displacement and rotation of the cable cross sections, assumed rigid in their own planes. The ensuing generalized strain parameters and curvatures retain the full geometric nonlinearities. By considering several case-study cables within the groups of taut and shallow cables, nonlinear equilibrium analyses are performed to investigate the effects of the cable bending and torsional stiffness for nontrivial boundary conditions. The full nonlinear formulation allows to estimate the size of the boundary layers as well as the stress states within them otherwise unknown adopting classical theories of purely stretchable cables. © 2015 Elsevier Ltd.

Versini P.-A.,French Scientific and Technical Center for Building | Ramier D.,CEREMA | Berthier E.,CEREMA | de Gouvello B.,French Scientific and Technical Center for Building
Journal of Hydrology | Year: 2015

At the building scale, the use of green roof has shown a positive impact on urban runoff (decrease and slow-down in peak discharge, decrease in runoff volume). The present work aims to study whether similar effects are possible at the basin scale and what is the minimum spreading of green runoff needed to observe significant impacts. It is particularly focused on the circumstances of such impacts and how they can contribute to storm water management in urban environment. Based on observations on experimental green roofs, a conceptual model has been developed and integrated into the SWMM urban rainfall-runoff model to reproduce the hydrological behaviour of two different types of green roof. It has been combined with a method defining green roofing scenarios by estimating the maximum roof area that can be covered.This methodology has been applied on a long time series (18. years) to the Châtillon urban basin (Haut-de-Seine county, France) frequently affected by urban flooding. For comparison, the same methodology has been applied at the building scale and a complementary analysis has been conducted to study which hydrometeorological variables may affect the magnitude of these hydrological impacts at both scales.The results show green roofs, when they are widely implemented, can affect urban runoff in terms of peak discharge and volume, and avoid flooding in several cases. Both precipitation - generally accumulated during the whole event- and the initial substrate saturation are likely to have an impact on green roof effects. In this context, the studied green roofs seem useful to mitigate the effects of usual rainfall events but turn out being less helpful for the more severe ones. We conclude that, combined with other infrastructures, green roofs represent an interesting contribution to urban water management in the future. © 2015 Elsevier B.V.

Merriaux P.,École Supérieure d'Ingénieurs en Génie Electrique | Dupuis Y.,CEREMA | Vasseur P.,University of Rouen | Savatier X.,École Supérieure d'Ingénieurs en Génie Electrique
2014 17th IEEE International Conference on Intelligent Transportation Systems, ITSC 2014 | Year: 2014

In this paper, we present a car self-localization approach based on free inputs. We propose to use wheel speeds, which is available on most car through the CAN bus, and community developed road maps. A particle filter framework is used to achieve self-localization on a graph-based representation of a road map. Our results suggests that self-localization and tracking are feasible with these two inputs at a really low computational cost. Car self-localization is achieved with an averaged 5 m accuracy within a 100 km drivable road map on a 12 km sequence. © 2014 IEEE.

Douet M.,Cerema
Transportation Research Procedia | Year: 2016

Change drivers across supply chains arise either from the production area or from the goods circulation area. A change in production can have a stronger impact on supply chains than a change in goods circulation. In particular, innovations inspired by sustainable development concerns which are firstly introduced within the production system, as some authors point out [Blanquart et al. (2008)], may greatly influence logistical organizations. Their introduction within supply chains requires more time [Roussat and Fabbe-Costes (2014)]. Change drivers may be institutional, commercial, technical, or managerial. Their types and features vary across periods and industries. Some may have quick-impact consequences, others will be slow in showing their effects on the whole supply chain. Three types of change drivers are currently main issues when consumer goods are concerned. Measures for preserving natural resources, with waste management and recycling of end-of-life products in order to minimize the consumption of non renewable resources, make up the first type of drivers. The second type is the ever wider use of online purchases, which disturbs B to B and B to C relationships as well as urban logistics and the last mile delivery terms. Thirdly, changes in logistical organizations of mass retailers may direct traffic flows via new logistics hubs. Food products are concerned by these change drivers in a specific way. Although some of them such as schools of fish may be renewable, natural resources must be protected. Reverse logistics processes are mainly confined to packaging because of the very nature of food. Distance purchases are steadily rising. While the market dependency upon mass retail firms is high, short supply circuits relying on local producers also attract consumers. Within the agri-food sector, the industry of fishery and aquaculture products is a major one feeding billion people around the world. In Europe, it employs approximately 267 000 full time equivalent workers [European Union (2014)], provides activity for hundreds of seaports, and positively contributes to local economies in peripheral shore areas. The paper therefore focuses on the situation of fishery and aquaculture products. The analysis highlights the situation of the whole supply chain within this specific food industry, allowing to achieve a non-fragmented view of it. It also clarifies, from a qualitative viewpoint, the respective role of sustainable development-based change drivers and the others, allowing to point out those giving impetus to changes. The analysis relies on a survey of academic literature and specialized publications, and on interviews with experts and key market players. It highlights the specific adaptations of supply chains within this valuable industry fully integrated in a global business world. It points out the first impacts of sustainable development concern decisions compared with those of other change drivers and illustrates how both kinds of impact interact to shape supply chain schemes. © 2016 The Authors.

Accident Analysis and Prevention | Year: 2015

Context: The objective of divided roads is to increase users safety by posting unidirectional traffic flows. It happens however that drivers proceed in the wrong direction, endangering themselves as well as other users. The crashes caused by wrong-way drivers are generally spotlighted by the media and call for public intervention. Objectives: This paper proposes a characterization of wrong-way driving crashes occurring on French divided road on the 2008-2012 period. The objective is to identify the actors that delineate between wrong-way driving crashes and other crashes. Method: Building on the national injury road crash database, 266 crashes involving a wrong-way driver were identified. Their characteristics (related to timing, location, vehicle and driver) are compared to those of the 22,120 other crashes that occurred on the same roads over the same period. The comparison relies on descriptive statistics, completed by a logistic regression. Results: Wrong-way driving crashes are rare but severe. They are more likely to occur during night hours and on non-freeway roads than other crashes. Wrong-way drivers are older, more likely to be intoxicated, to be locals, to drive older vehicles, mainly passenger cars without passengers, than other drivers. Perspectives: The differences observed across networks can help prioritizing public intervention. Most of the identified WW-driving factors deal with cognitive impairment. Therefore, the specific countermeasures such as alternative road signs should be designed for and tested on cognitively impaired drivers. Nevertheless, WW-driving factors are also risk factors for other types of crashes (e.g. elderly driving, drunk driving and age of the vehicle). This suggest that, instead of (or in addition to) developing WW-driving specific countermeasures, managing these risk factors would help reducing a larger number of crashes. © 2014 Elsevier Ltd. All rights reserved.

Champenoy D.,CEREMA | Corfdir A.,University Paris Est Creteil | Corfdir P.,Dir Est
European Journal of Environmental and Civil Engineering | Year: 2014

French practice for assessing the risk of distortional buckling of composite bridges is based on the Engesser or Lazard methods which assimilate the phenomenon to in-plane buckling of the compressed flanges. A flange is modelled as a uniformly-compressed rectangular-section beam of constant depth with periodic (Lazard) or continuous (Engesser) elastic restraints. The purpose of the study is to consider more realistic assumptions in order to optimize flange dimensions, bearing in mind the fact that the Eurocodes are more severe with respect to instability phenomena than the current French regulations. In particular, the study addresses the case of variable compressive force with variable flange thickness. The results are presented as designs chart for design use. © 2014 Taylor & Francis.

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