Aix-en-Provence, France
Aix-en-Provence, France

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Beze L.E.,Aix - Marseille University | Rose J.,Aix - Marseille University | Mouillet V.,CETE Mediterranee | Farcas F.,IFSTTAR | And 3 more authors.
Fuel | Year: 2012

Vanadium is well known to promote the ageing of bitumen through oxidation of the carbon matrix. Nevertheless the mechanism by which vanadium may induce organic compound oxidation is not clearly understood. Then the evolution of the speciation of the vanadium into bitumen matrix with ageing was studied. V-K edge XANES (X-ray Absorption Near Edge Structures) experiments showed no evolution of the oxidation state and geometry of V although all bitumen oxidation indexes indicated intense ageing, thus suggesting that vanadium can promote the bitumen oxidation through catalytic phenomena. Micro-XANES experiments at the V-K edge combined with micro-X-ray Fluorescence (XRF) showed that, in a laboratory model of hot reclaimed bituminous mixes, the presence of aggregates (CaCO 3 particles) enhanced the oxidation of bitumen, without however affecting the oxidation state of V. As a consequence, the vanadium speciation during bitumen ageing cannot be used as a tracer of the bitumen ageing and mixing between fresh and reclaimed bitumen. © 2012 Elsevier Ltd. All rights reserved.

Bertrand E.,CETE Mediterranee | Duval A.-M.,CETE Mediterranee | Regnier J.,CETE Mediterranee | Azzara R.M.,Italian National Institute of Geophysics and Volcanology | And 7 more authors.
Bulletin of Earthquake Engineering | Year: 2011

During the microzonation studies of the April 6th, 2009 L'Aquila earthquake, we observed local seismic amplifications in the Roio area-a plane separated from L'Aquila city center by mount Luco. Six portable, digital instruments were deployed across the plain from 15 April to mid-May 2009. This array recorded 152 aftershocks. We analyzed the ground motion from these events to determine relative site amplification within the plain and on surrounding ridges. Horizontal over vertical spectral ratio on noise data (HVSRN), aftershock recordings (HVEQ) and standard spectral ratio (SSR) showed amplifications at 1.3 and 4.0 Hz on quaternary deposits. Seismic amplifications in the frequency range of 4 and 6 Hz were also observed on a carbonate ridge of Colle di Roio, on the northwestern border of the plateau. A small amplification was noticed near the top of mount Luco, another rocky site. Large discrepancies in the amplification levels between methods have been observed for these sites, but the HVSRN, HVEQ and SSR gave similar results at the stations located in the Roio plain. On the rocky sites, the SSR was more reliable than the HVSRN at estimating the transfer function of the site, even if the resonance frequency seemed to be well detected by the latter method. © 2011 Springer Science+Business Media B.V.

Bonilla L.F.,University Paris Est Creteil | Tsuda K.,Shimizu Corporation | Pulido N.,Japan National Research Institute for Earth Science and Disaster Prevention | Regnier J.,CETE Mediterranee | Laurendeau A.,ISTERRE
Earth, Planets and Space | Year: 2011

We analyzed the acceleration time histories recorded by the K-NET and KiK-net stations of the M w 9 Tohoku Earthquake in order to investigate site response issues related to near-source effects. Time-frequency analysis of K-NET stations in the Miyagi prefecture, closest to the rupture area, show that sites having a V s30 <400 m/s present a combination of deamplification at frequencies higher than 5 to 10 Hz and cyclic mobility (high acceleration peaks riding over a low frequency carrier). This suggests strong nonlinear site response at these stations. Furthermore, using KiK-net data we are able to compute borehole transfer functions from the mainshock and events having small PGA values from the local dataset. The ratio between weak-motion and strong-motion borehole transfer functions constitutes an indicator of nonlinear site response. This ratio reveals strong dependence on V s30 and shows that widespread nonlinear behavior took place during this large earthquake. Copyright © The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS).

Granie M.-A.,IFSTTAR MA | Brenac T.,IFSTTAR MA | Montel M.-C.,IFSTTAR MA | Coquelet C.,IFSTTAR MA | And 3 more authors.
Advances in Transportation Studies | Year: 2013

Purpose: Taking all users of the road system into account - notably those who use non-motorized modes of transportation - is a major challenge for urban engineers when designing roads and public spaces. And yet, although a body of knowledge exists concerning the effects of the environment on pedestrian accidentology, so far very little research has been carried out on the perception pedestrians have of the road environment (structure of buildings, vegetation, etc.) and its influence on decision-making when crossing. This exploratory research aims at studying this perception through a qualitative approach. Methods: We used the focus group method to study the perception of 20 two-way street environments with a certain level of diversity from the point of view of buildings (type, density, and heterogeneity), activities, position in relation to the city center, width of the sidewalks and type of traffic. The participants in the two focus groups were 11 regular or occasional pedestrians. Results: The verbal material obtained is analyzed in terms of perception of the environment, inferences about driver behavior (notably toward pedestrians), and influence on the pedestrian crossing behavior. Pedestrians prefer environments in which they have the "upper hand" or environments that are highly predictable. Conclusions: The results suggest a few tendencies or lines of approach concerning the design of spaces that make street crossing more comfortable for pedestrians. They also show that the focus group method is of great interest for studying the perception and interpretation of urban environments.

Godano M.,University of Nice Sophia Antipolis | Larroque C.,University of Nice Sophia Antipolis | Bertrand E.,CETE Mediterranee | Courboulex F.,University of Nice Sophia Antipolis | And 6 more authors.
Tectonophysics | Year: 2013

During one month, in October and November 2010, the region of Sampeyre (Western Alps, Italy) was struck by a seismic activity of several hundred events. The location of 287 events recorded at least by three stations showed a diffuse swarm ranging between 8 and 13. km depth. The number of earthquakes in the database was increased thanks to a detailed analysis of the continued recordings of the nearest station (DOI) which allowed identifying 2612 earthquakes. The temporal distribution of the seismicity is characterized by the alternation of active and quiescent periods. Moment magnitude was computed for 730 events by a P wave spectral analysis of the DOI station data. The estimated magnitudes range between 0.7 and 3.15. The b-value of the cumulated frequency-magnitude distribution is around 1.4. Spatio-temporal analysis of the located earthquakes highlighted an overall northward migration of the seismicity. From spatio-temporal criteria, the seismicity was divided in three clusters. Each cluster is characterized by its own focal mechanism family. The stress tensor determined from the focal mechanisms indicates probable stress heterogeneities at small spatial scale. The observed migration of the seismicity could be compatible with earthquake triggering by fluid diffusion processes. © 2013 Elsevier B.V.

Regnier J.,CETE Mediterranee | Cadet H.,ISTerre | Cadet H.,Pierre Mendès-France University | Fabian Bonilla L.,University Paris Est Creteil | And 2 more authors.
Bulletin of the Seismological Society of America | Year: 2013

This article investigates the effects of the nonlinear behavior of soils on site response, through various earthquake recordings from the KiK-net database in Japan. This network is composed of more than 688 surface-borehole instruments, from which a characterization of the shear- and compressive-wave velocity profiles down to the borehole depth is available. We selected events with a peak ground acceleration (PGA) at the downhole station of < 10 cm=s2 in order to characterize the linear soil behavior by computing the surface to downhole spectral ratios at each site. Modifications of site-response curves computed with strong events (PGA > 50 cm=s2) compared to the linear characterization are supposed to be caused by nonlinear soil behavior. To describe the effects of soil nonlinear behavior on site response per event, we propose the percentage of modification (either amplification or deamplification) of the site-response curve compared to the linear evaluation (PNLev, percentage of nonlinearity) and the associated shift frequency (Shev). These parameters are used to estimate the probability that nonlinear site response is significantly different that the linear counterpart. We find that, regardless the site, this probability is important even for low input-motion PGA (values equal to or larger than 30 cm=s2 at downhole sensor). This indicates that nonlinear soil behavior must be taken into account in site-response evaluation for moderate to strong motion. In addition, for 54 sites of the KiK-net database that have recorded at least two strong events (PGA at the downhole station > 50 cm=s2), we define four additional parameters that characterize the effects of soil nonlinear behavior on site responses for each site: (1) a PGA threshold (PGAth), defined as the PGA value for which PNLev is higher than 10%; (2) a site-specific PNL for a PGA of 50 cm=s2 (PNLsite); (3) a site-specific shift of the predominant frequency for a PGA of 50 cm=s2 (Shsite); and (4) a frequency from which we observe deamplification between nonlinear and linear site responses (fNL). We observe that nonlinear soil behavior can increase the amplification at frequencies below fNL. We find that fNL lies in between the fundamental and the predominant resonance frequencies of the site response and that sites having VS contrast close to the surface trigger nonlinear behavior at a lower input-motion PGA threshold. These results suggest that nonlinear behavior occurs mostly in the superficial soil layers. Furthermore, by investigating the nonlinear behavior of soils on earthquake horizontal-to-vertical spectral ratios at the surface, we find that they can give satisfactory results (equivalent to the analysis of borehole site responses) for the evaluation of the fNL frequency and shift frequency (Shsite), which indicates that part of the results obtained in this study can be extended to other databases without downhole sensors.

Two practical aspects of undrained cyclic triaxial test procedures are examined. The first one concerns the rate of loading, which is always significantly greater than that applied during monotonic loading tests on silty and clayey soils. The second procedure concerns the level of static stresses applied during cyclic loading, in order to explain that the yield strength criteria are more readily reached in tension during a strictly alternating test protocol. A summary of testing procedures is presented, along with examples of test results, before offering a few concluding remarks.

This article describes a natural soil identification method based on data measured using a piezocone (CPTu) and presents an application to soils from France's Var delta plain. This method proceeds in two stages: penetrometer point resistance is first broken down into an isotropic part and a deviatoric part by taking into account water pressure and both the drained and undrained strength measured using the triaxial device on soil samples that had been previously cored in situ. This decomposition serves to classify soils by distinguishing clayey and silty finegrained soils, in which high water pressure develops, from the sandy soils where these pressures are either close to the hydrostatic pressure or else negative. The next stage consists of identifying sensitive sandy soils, which feature limited compactness, low strength and are exposed to the risk of liquefaction, by means of analyzing the unit lateral friction and effective cone resistance.

Vivier A.,SYSTRA | Charles P.,Électricité de France | Davi D.,CETE Mediterranee
Bulletin des Laboratoires des Ponts et Chaussees | Year: 2013

This paper presents an application of dynamic time analysis to a real problem: optimizing the reinforcement of Caronte bridge against earthquakes. The assessment of reinforcement techniques led to a solution based on shock-absorbers. On the occasion of this study, time analysis methods were used, which were the only methods allowing for rigorously accounting for shock-absorbers in a complex structure. Preliminary design tools were developed for defining the characteristics of the devices to be used and performing the dynamic time analysis of the structure. They converged towards a solution based on viscous shock-absorbers. Besides, this study highlighted the advantages of such devices for the reinforcement of structures against earthquakes and the interest and feasibility of dynamic time analyses, sometimes considered as too complex.

Granie M.-A.,IFSTTAR LMA | Brenac T.,IFSTTAR LMA | Montel M.-C.,IFSTTAR LMA | Millot M.,CETE Mediterranee | Coquelet C.,IFSTTAR LMA
Accident Analysis and Prevention | Year: 2014

The objective of this experimental study is to identify the differentiation made by pedestrians, in their crossing decision, between various urban environments, notably in terms of perception of walking pleasantness and safety. This experiment further aims to identify the environmental features that pedestrians take into account and the inferences they develop and use to explain their road crossing decision. Sets of photographs presenting five different environments (city center, inner suburbs, public housing in the outskirts, commercial zone in the outskirts and countryside) were presented to 77 participants divided up into three age groups (pre-adolescents, young and middle adults). Their decision to cross or not, their perception of pleasantness and safety, and the elements they take into account to make a decision were collected for each environment presented. The quantitative results show the pedestrians' perceptions of the pleasantness and safety of public spaces, in terms of walking, largely vary with urban environments. Moreover, the crossing decision significantly varies according to the environment. Pedestrians were significantly more inclined to take the decision to cross in city center than in the other sites presented. The qualitative analysis of the interviews shows that the presence and function of the buildings, the quality of the sidewalks and the marked parking spaces are key factors to explain their crossing decision, by enabling them to infer the density of pedestrians and traffic and the vehicle speed. © 2014 Elsevier Ltd.

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