Nantes, France
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Balayssac J.-P.,Toulouse 1 University Capitole | Laurens S.,Toulouse 1 University Capitole | Arliguie G.,Toulouse 1 University Capitole | Breysse D.,University of Bordeaux 1 | And 3 more authors.
Construction and Building Materials | Year: 2012

The management and maintenance of the built heritage is one of the main concerns of the owners of concrete structures. Engineers wish to obtain quantitative information about concrete properties and their variability. Non-destructive testing (NDT) is very popular in this context as it quickly provides relevant information on the integrity and ageing of the material, but several kinds of indicators representative of the concrete condition need to be evaluated. Combining NDT methods is currently considered as one of the most appropriate ways to improve the quality of the diagnosis of concrete structures. This paper describes a French project named SENSO (Strategy of non-destructive evaluation for the monitoring of concrete structures) devoted to developing a methodology for the non-destructive evaluation of concrete based on a multi-technique approach. The main objective of the project was to define the sensitivity of the techniques (ultrasonics, radar, capacitive and resistivity) and the variability of the evaluation for each indicator concerned. To achieve this, a large experimental programme, involving a representative range of concretes and several indicators, was carried out. A database linking the measured values by NDT and the indicators allowed the different measurements to be distinguished in terms of quality (linked to the variability) and in terms of relevance for the characterisation of each indicator. The added value of the combination of techniques was obtained by means of data fusion. The methodology developed in laboratory conditions, involving both evaluation of the indicators and data fusion, was tested on full-scale models in which the indicators were not fully controlled. © 2012 Elsevier Ltd. All rights reserved.


Chapeleau X.,PRES LUNAM | Sedran T.,PRES LUNAM | Cottineau L.-M.,PRES LUNAM | Cailliau J.,British Petroleum | And 3 more authors.
Engineering Structures | Year: 2013

Ballastless track structure are presently seen as an attractive alternative to conventional ballast. A new model was designed and a real-scale mockup was built and tested in fatigue test at IFSTTAR laboratory. To verify numerical simulations, the railway structure was monitored by conventional strain gages. A distributed fiber-optic strain sensing based on Rayleigh backscatter was also tested in this experiment. Fiber-optic cables were used as long-gage sensors and they were embedded in the concrete slabs of the structure. Firstly, we verified that the sensors were enough mechanical and chemical resistant for withstanding the stresses and the caustic environment experienced during concrete pouring process. Secondly, we validated the strain profiles measurements by comparison with the values obtained by strain gages. A good agreement was found throughout the duration of the fatigue test of 10 million cycles. Moreover, some cracks were observed early during the fatigue test. It is important to be able to monitor them during the service of ballastless track line. We showed that cracks can be detected and localized by fiber-optic distributed strain measurements. Finally, this experiment demonstrates that fiber-optic distributed strain sensing technique based on Rayleigh backscatter is a promising sensing technique to monitor ballastless track structures and more generally, civil engineering structures. © 2013 Elsevier Ltd.


Emmanuel I.,PRES LUNAM | Andrieu H.,French National Center for Scientific Research | Leblois E.,IRSTEA | Flahaut B.,PRES LUNAM
Journal of Hydrology | Year: 2012

The main objective of this paper is to characterize the spatial and temporal variability of different types of rain events at scales that are consistent with urban hydrological applications. In this way, a total of 24 rain periods have been analyzed according to a geostatistical approach. This analysis has focused on the non-zero rainfall variogram. The studied rain periods were recorded by the weather radar of Treillières (10. km north of Nantes, France) in 2009. This radar device provides rainfall radar images with a high level of spatial resolution (250. m × 250. m) and instantaneous temporal resolution. Results indicated four different types of rainfall fields, which display very different variability scales, including double structures within the same field. These four types of rainfall fields can be characterized by their climatological variograms, as calculated for increasing time resolutions: instantaneous, 5. min, 15. min, and 30. min, thus making it possible to estimate the decorrelation distance (i.e. range). This study highlights the benefit of radar images featuring high temporal and spatial resolution, which in turn allow studying small-scale variability. © 2012 Elsevier B.V.


Ramond-Roquin A.,PRES LUNAM | Ramond-Roquin A.,Laboratory of Ergonomics and Epidemiology in Occupational Health | Pecquenard F.,PRES LUNAM | Schers H.,Radboud University Nijmegen | And 4 more authors.
Family Practice | Year: 2015

Background. Better insight into frequent comorbidities in patients with chronic (= 3 months) low back pain (LBP) may help general practitioners when planning comprehensive care for these patients. Objective. To prospectively study the prevalence of psychological, social, musculoskeletal and somatoform disorders in patients presenting with chronic non-specific LBP to general practitioners, in comparison to a contrast group of patients consulting in the same setting. Methods. This case-control study is embedded in a historical cohort, based on a primary care practice-based research network. All the health problems presented by the patients were prospectively coded according to the international classification of primary care between 1996 and 2013. The prevalence of psychological, social, musculoskeletal and somatoform disorders presented by the adult patients from 1 year before the onset of chronic LBP to 2 years after onset was compared to that of matched patients consulting without LBP, using conditional logistic regressions. Results. The 1511 patients with chronic LBP more often presented musculoskeletal disorders than the contrast group during the year before the onset of LBP and during the second year after it, with odds ratios (95%confidence intervals) of 1.39 (1.20-1.61) and 1.56 (1.35-1.81), respectively. They did not more often present psychological, social or non-musculoskeletal somatoform disorders. Conclusions. General practitioners should consider all the musculoskeletal symptoms when caring for patients with chronic LBP. Rather than systematically screening for specific psychological, social or somatoform disorders, they should consider with the patient how LBP and any type of potential comorbidity interfere with his/her daily functioning. © The Author 2015. Published by Oxford University Press. All rights reserved.


PubMed | Australian National University, Laboratory of Ergonomics and Epidemiology in Occupational Health, University of Amsterdam, Radboud University Nijmegen and PRES LUNAM
Type: Journal Article | Journal: Family practice | Year: 2015

Better insight into frequent comorbidities in patients with chronic ( 3 months) low back pain (LBP) may help general practitioners when planning comprehensive care for these patients.To prospectively study the prevalence of psychological, social, musculoskeletal and somatoform disorders in patients presenting with chronic non-specific LBP to general practitioners, in comparison to a contrast group of patients consulting in the same setting.This case-control study is embedded in a historical cohort, based on a primary care practice-based research network. All the health problems presented by the patients were prospectively coded according to the international classification of primary care between 1996 and 2013. The prevalence of psychological, social, musculoskeletal and somatoform disorders presented by the adult patients from 1 year before the onset of chronic LBP to 2 years after onset was compared to that of matched patients consulting without LBP, using conditional logistic regressions.The 1511 patients with chronic LBP more often presented musculoskeletal disorders than the contrast group during the year before the onset of LBP and during the second year after it, with odds ratios (95%confidence intervals) of 1.39 (1.20-1.61) and 1.56 (1.35-1.81), respectively. They did not more often present psychological, social or non-musculoskeletal somatoform disorders.General practitioners should consider all the musculoskeletal symptoms when caring for patients with chronic LBP. Rather than systematically screening for specific psychological, social or somatoform disorders, they should consider with the patient how LBP and any type of potential comorbidity interfere with his/her daily functioning.


The present work aims to quantify the effects of neglecting rainfall spatial variability for runoff modelling at the outlet of catchments ranging from ten to several hundred km (of urban or peri-urban type). We have proceeded by simulation in order both to overcome modelling and measurement errors, in addition to controlling rainfall variability and the characteristics and hydrological behavior of catchments. For this purpose, it has been used a simulation chain including a stream network model, a rainfall simulator and a distributed hydrological model (with four production functions and a distributed transfer based on the Hayami model). It has also been decided not to conduct an exhaustive investigation but instead a study of contrasting situations. Results showed the difficulty to obtain general conclusions from studying just a few events and thus contribute to explain the divergent conclusions drawn in the literature. Moreover, the proposed methodology revealed a number of trends. For the different studied rainfall configurations, the effects of neglecting rainfall spatial variability appear to be significant in situations where rainfall contrasts are created and maintained over the catchments. Such situations were identified for three scenarios: 1) the dimensionless "rainfall field velocity to catchment flow celerity" ratio is close to 1; 2) the rainfall field direction is perpendicular to the main catchment flow direction; and for 3) a Horton or SCS production function. At last, in order to verify that simulation results are close to reality, all results will have to be confronted to those obtained on real catchments with some real rainfall measurements. © Société Hydrotechnique de France, 2016.


Madieta E.,PRES LUNAM | Symoneaux R.,PRES LUNAM | Mehinagic E.,PRES LUNAM
International Journal of Food Science and Technology | Year: 2011

Texture profile analysis (TPA) is widely used to assess the textural properties of fruit. However, test parameters may potentially affect TPA results. This work studies the influence of the degree of deformation and crosshead speed on the mechanical parameters of apple measured by TPA. In this study, the degree of deformation ranged from 5% to 17.8% and the crosshead speed from 10 to 90mmmin-1. Eight parameters were extracted from the analysis of force-displacement and force-time curves. For each parameter, the mean value and the coefficient of variation (CV) were examined. A central composite design that simultaneously takes into account both input variables, the degree of deformation and crosshead speed, was implemented. It appears that the linear and the quadratic effects of the degree of deformation make it the major variable. However, neglecting the effects (linear and quadratic) of the crosshead speed might be disastrous since they significantly affect parameters such as cohesiveness, gumminess and work 2. Moreover, the CV of hardness 1 depends mainly on the interaction between the degree of deformation and crosshead speed. © 2011 Groupe ESA.


Cordelle A.,PRES LUNAM | Chapeleau X.,PRES LUNAM | Drissi-Habti M.,PRES LUNAM
Revue des Composites et des Materiaux Avances | Year: 2013

Composite materials are increasingly used as building materials, especially in civil engineering. However their fatigue behavior, especially when submitted to bending stress is still poorly understood. Thus, the development of appropriate structural health monitoring techniques are highly needed. The embedment of optical fiber sensors in a material obtained by pultrusion with the scope of monitoring the deformation of composite structures throughout its lifetime is one of the most promising way to get what is commonly called smart materials. This study focuses on the the evaluation of the integrity of the instrumentation with Fiber-Bragg-Gratings that is embedded in composites, particularly in terms of quasi-static loading as well as fatigue. The final goal is to validate this technique so that it can apply successfully in SHM of large dimensions structures (20m x 7m). © 2013 Lavoisier.


Chapeleau X.,Pres LUNAM | Drissi-Habti M.,Pres LUNAM
Proceedings of the 6th European Workshop - Structural Health Monitoring 2012, EWSHM 2012 | Year: 2012

In this work, composite materials were instrumented by optical fiber sensors with the scope to monitor the instrumentation of pultruded profile made out of composite materials. Then after, using Fiber-Bragg Gratings, were used to monitor strain under quasi-static and fatigue loading under 3-point bending. Results show that optical fiber sensors perform well in either cases. The results that are reported are part of the French Program decid2 aiming at building a large dimensions plateform (20m x 3,5m, DECID2 Project).


Terrien N.,Pole EPI | Dhamene F.,ECW | Zejli H.,ALTEN | Habti M.D.,PRES LUNAM
7th European Workshop on Structural Health Monitoring, EWSHM 2014 - 2nd European Conference of the Prognostics and Health Management (PHM) Society | Year: 2014

This paper is dealing with the development of a structural health monitoring (SHM) system implemented on a composite footbridge during the regional project "Pays de la Loire" called DECID2. The SHM system was made out of complementary techniques: strain sensors based on optical fibers (out of concern in this present work) and ultrasonic techniques that are presented in this document. Due to the huge size of the composite bridge (20 m ∗ 3 m), only its most critical areas are monitored as the assembling parts and the most solicited areas. To access the structural integrity of the footbridge, two complementary monitoring strategies were presented in this paper: - a real-time acoustic emission monitoring system to detect fibre breaks, - and a monitoring system using guided waves to evaluate the resin degradation. Both of these SHM systems use the same miniature ultrasonic patches that are used alternately as acoustic emission sensors and as ultrasonic guided waves actuators. The first step of this work was to develop these patches, and then to set up each monitoring systems and characterize their damage sensitivity. Finally, two composite footbridges were built at the EMC2 Technocampus and IFSTTAR in France to serve as demonstrators. Copyright © Inria (2014).

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