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6th International Conference on Accelerated Pavement Testing , NANTES, FRANCE, 27-/09/2021 - 29/09/2021; The concept of truck platooning is to take advantage of the connectivity technologies and automated driving support systems to link trucks in close formation (convoy) in order to increase transport efficiency, reduce fuel consumption and gas emissions while improving road safety. However, closely guided trucks following each other could have a different impact on road structures than the usual truck traffic. Notably, different studies with traffic simulators highlight the significant effect of the wander pattern of traffic on the damage observed on test road structures. On the other hand, the positioning systems could offer the opportunity to choose an optimized wander pattern of the trucks within the platoons, especially designed to mitigate the overall damage. In this context, the study reported in this paper addresses, through numerical simulations, the multi-loading effects of truck platoons on road structures for different configurations of wander patterns. The aggressiveness of these patterns is evaluated on the basis of the viscoelastic response of the pavement structures (strain field) computed using software ViscoRoute\textcopyright 2.0. Finally, recommendations on the choice of wander pattern configurations to be tested on APT facilities are proposed.

International audience; Plan :1. Un litige sans précédent2. L'incertitude attachée à la notion « d'actualisation »3. Quid de l'anatocisme ?4. PlanI - « L'actualisation », une notion « venue d'ailleurs »5. L'arrêt Manfredi6. Une notion d'économie7. Les mécanismes existants pour réparer l'effet préjudiciable du temps8. Articulation de « l'actualisation » avec ces mécanismes ?9. Flottement de la jurisprudence antérieure10. Un débat juridique occulté ?II - La capitalisation des indemnités actualisées suppose une demande expresse11. Les deux thèses en présence : régime sui generis ou droit commun ? 12. Applicabilité de l'ancien article 1154 et nécessité d'une demande expresse13. Les inconnues persistantesIII - La soumission souhaitable de la réparation de l'effet préjudiciable du temps au droit commun de la responsabilité civile14. Raisonner selon la trilogie perte éprouvée/gain manqué/perte de chance15. Rompre avec la logique forfaitaire et soumettre la réparation des effets préjudiciables du temps au principe de réparation intégrale.

One of the components of the fifth generation road is its capacity to communicate with its network manager in order to improve maintenance. The aim of the experimental instrumentation presented in this study is to monitor the evolution of characteristic damage in mixed structures: nonvisible cracks rising from the hydraulic base towards the coated pavement surface. The objective of the sensors is to be able to anticipate damage before it reaches the surface. As temperature is also being measured, it is possible to use this data to communicate with users concerning the potential risk of ice forming on the road. The first measurements have been compared with a theoretical model of the structure, and the continuous acquisition of signals will enable the network manager to monitor the behaviour of the road.

Damage diagnosis is a fundamental task for structural health monitoring (SHM). With the statistical sensitivity-based damage localization approach, a residual vector is computed from vibration measurements in the reference and the damaged state. The residual is analyzed statistically in hypothesis tests with respect to change directions defined by the sensitivities of the structural parameters associated to elements of a finite element (FE) model of the investigated structure. If the test for a parameter reacts, then the respective element of the structure is indicated as damaged. This approach offers a very generic and theoretically sound framework to analyze parametric changes in systems, and takes into account the intrinsic statistical uncertainty related to measurement data. Depending on the definition of the residual and of the parameterization, the approach offers a simple computation of the test statistics directly from the measurement data in the damaged system, without the need of system identification. Since an FE model is used, the approach is applicable on arbitrary structures, while no model updating is required and therefore the requirements on the FE model accuracy are less strict. While the theoretical framework has been developed previously, it lacked robustness so far for an application on real structures. The purpose of this paper is the development of this framework into a working damage localization method that is applicable on real data from complex structures. To achieve this goal, robust hypothesis tests are used, the sensitivity computation of the residual is revisited for more precision thanks to reduced modal truncation errors, and an adequate clustering approach is proposed for the case of a high-dimensional FE parameterization for complex structures. Furthermore, several robustness properties of the method are proven. Finally, an application of this framework is shown for the first time on experimental data for damage localization, namely in an ambient vibration test of a 3D steel frame at the University of British Columbia.

This paper proposes a numerical method to model wave scattering by local inhomogeneities in elastic open waveguides. The damaged zone of the waveguide and its vicinity are described by a finite-element model. This model is coupled on the cross-section boundaries to a modal representation of the field propagating along the waveguide axis in the undamaged parts, yielding transparent boundary conditions. However, open waveguides are unbounded in the transverse direction, which complicates both the numerical resolution and the physical analysis. Theoretically, the wave fields are described by a discrete sum of trapped modes and two continuous sums on radiation modes. The latter is sometimes approximated by a discrete sum of leaky modes, which grow at infinity in the transverse direction. In this paper, a Perfectly Matched Layer (PML) of finite thickness is introduced to absorb outgoing waves in the transverse direction, yielding three types of discrete modes: trapped modes, leaky modes and PML modes (PML modes oscillate mainly inside the layer and are non-intrinsic to the physics). Two numerical test cases are considered: the scattering at the junction between a closed and an open cylindrical waveguides and the scattering by an axisymmetrical notch. Good agreement with literature results is found. In particular, the influence of PML modes on the scattered field is highlighted through numerical tests. Due to the lack of power orthogonality of leaky modes, it is also shown that the modal cross power can become significant, which complicates the scattering analysis of open waveguides. Finally, the generality of the proposed method is discussed through a three-dimensional test case considering an embedded bar with an oblique break.

FLOODrisk 2016, 3rd european conference on flood risk management, LYON, FRANCE, 17-/10/2016 - 21/10/2016; Flash floos monitoring systems developed up to now generally enable a real-time assessment of the potential flash-floods magnitudes based on highly distributed hydrological models and weather radar records. The approach presented here aims to go one step ahead by offering a direct assessment of the potential impacts of flash floods on inhabited areas. This approach is based on an a priori analysis of the considered area in order (1) to evaluate based on a semi-automatic hydraulic approach (Cartino method, Pons et al. 2014) the potentially flooded areas for different discharge levels, and (2) to identify the associated buildings and/or population at risk based on geographic databases. This preliminary analysis enables to build a simplified impact model (discharge-impact curve) for each river reach, which can be used to directly estimate the importance of potentially affected assets based on the outputs of a distributed rainfall-runoff model. This article presents a first case study conducted in the Gard region (south eastern France). The first validation results are presented in terms of (1) accuracy of the delineation of the flooded areas estimated based on the Cartino method and using a high resolution DTM, and (2) relevance and usefulness of the impact model obtained. The impacts estimated at the event scale will now be evaluated in a near future based on insurance claims data provided by CCR (Caisse Centrale de Réassurrance).; Présentation d'un modèle de prévision des crues soudaines et de résultats de validation à partir de sinistres enregistrés par les compagnies d'assurance.

International audience; In this paper are reported the results of an experimental campaign carried out on a post tensioned concrete beam with the aim of investigating the possibility to detect early warning signs of deterioration basing on static and/or dynamic tests. The beam was tested in several configurations aimed to reproduce several different phases of the 'life' of the beam: the original undamaged state, increasing loss of tension in the post tensioning cables, a strengthening intervention carried out by means of a second tension cable, formation of further cracks on the strengthened beam. Responses of the beam were measured by an extensive set of instruments consisting of accelerometers, inclinometers, displacement transducers, strain gauges and optical fibres. The paper discusses the tests program and the dynamic characterization of the beam in the different damage scenarios. The modal properties of the beam in the different phases were recovered basing on the responses recorded on the beam during sine-sweep and impact hammer tests. The variation of the first modal frequency was studied to investigate the sensitivity of this parameter to both the cracking of the concrete section and the tension in the cables and also to compare results given by different types of experimental tests.

Les Eurocodes définissent la robustesse structurale comme 'l'aptitude d'une structure à résister à des événements tels que les incendies, les explosions, les chocs ou les conséquences d'une erreur humaine, sans présenter de dégâts disproportionnés par rapport à la cause d'origine'. Cette définition permet d'intégrer explicitement des concepts de défaillances locales (dommages de faible ampleur) et globale (dommages associés à des conséquences structurales majeures). Cet article propose un cadre probabiliste pour quantifier la robustesse structurale en mesurant l'impact d'une défaillance localisée sur la défaillance globale du système. La démarche proposée consiste à identifier les chemins de défaillance les plus probables partant d'une défaillance localisée. L'écart entre les défaillances locale et globale dans le chemin de défaillance avec la plus grande probabilité, considéré comme le chemin de référence, est alors quantifié pour construire des indices de robustesse. L'identification des chemins de défaillance les plus probables est effectuée au travers de la méthode des 'branches et bornes'. Deux exemples d'application sont considérés pour illustrer la méthodologie proposée.

Following the Mw 7.3 Martinique earthquake, November 29th, 2007, a post-seismic survey was conducted by the Bureau Central Sismologique Français (BCSF) for macroseismic intensities assessment. In addition to the inventories, ambient vibration recordings were performed close to the particularly damaged zones in the free-field and the buildings. The objective of the paper is to show the relevancy of performing ambient vibration recordings for post-earthquake surveys. The analyses of the recordings aim at explaining the variability of the damages through site effects, structure vulnerability or resonance phenomena and to help the characterization of the post-seismic building integrity. In three sites prone to site effects, we suspect damage to be related to a concordance between soil fundamental frequency and building resonance frequency. Besides, the recordings of ambient vibrations at La Trinité hospital before and after the earthquake allow us to quantify the damage due to earthquake in terms of stiffness loss.

A large amount of researches and studies have been recently performed by applying statistical methods for vibration-based damage detection. However, the global character inherent to the limited number of modal properties issued from operational modal analysis may be not appropriate for early damage, which has generally a local character. The present paper aims at detecting this type of damage by using static SHM data and by assuming that early damage produces dead load redistribution. To achieve this objective a data driven strategy is proposed, consisting in the combination of advanced multivariate statistical methods and quantities, such as principal components, symbolic data and cluster analysis. From this analysis it was observed that, under the noise levels measured on site, the proposed strategy is able to automatically detect stiffness reduction in stay cables reaching at least 1%.

Structural health monitoring (SHM) provides accurate in situ information and its use in management of infrastructures is an important challenge. For a large population of assets, SHM information may be composed of numerous and various types of data. The crucial issue is that the quantity and heterogeneity of information may finally prevent from efficiently correlating collected data and informing the performance metrics of interest. Data mining concepts offer possibilities of analyzing and correlating complex (i.e., heterogeneous) data. The fusion of these data to get new knowledge requires using symbolic data which are an extension of standard numerical or categorical data. Symbolic Data Analysis (SDA) is illustrated in this paper by the study of the degradation problems occurring on nuclear power plant cooling towers. This paper presents the suitability of SDA for structural degradation analysis, combination of heterogeneous measures, description of the correlations between them, and classification of the degradations. Complex data

Dynamical assessment is often employed to evaluate structures in civil engineering. This non-destructive surveillance technique became an attractive approach in order to show the existence of damages and to predict its location. The modal parameters of the structure are determined by modal identification methods without any prior knowledge of the nature of the excitation. The application of damage detection and localization techniques is performed by comparing the variation of the modal parameters between the states before and after damage. To do so, various methods can be used. In this paper, only the mode shape curvature and strain energy methods are considered because of the computation of the curvature in theirs algorithms. A discretization of the structure is needed on account of the location of the sensors and their number which generates a drawback. Commonly, the finest the discretization the better the approximate solution will be sufficiently accurate. However, several experimental analyses have shown this fact cannot be established in the damage detection domain. Indeed, this computation leads us to truncation errors including the effects of measurement noise, which leads to a loss of accuracy at the time of damage detection and localization. This paper aims to show the possibility to improve the accuracy of both proposed methods. The idea consists in minimizing the effect of noise and truncation errors by finding an optimal discretization interval. The values of this interval depend on several parameters, boundary conditions, bending mode, noise level. Numerical tests are carried out considering the presence of noise and damage simulations are performed on the tested beam. Furthermore, using the SysIdent-LCPC toolbox, several experimental tests are presented for the Merlebach’s beam in order to test the quality and the efficiency of the selected discretizations. The results are encouraging in order to go forwards the investigations in this direction.

To model the three dimensional response of reinforced concrete structures subject to complex loadings, the local constitutive model for concrete have to account for different nonlinear mechanisms such as :Stiffness decrease due to cracks and stiffness recovery due to closing cracks under cyclic loadings, inelastic strains due to the material heterogeneity, frictional sliding due to the cracked surfaces rugosity. In this contribution, a three dimensional behaviour constitutive set of equations for modelling the mechanical response of quasi brittle materials such as concrete is presented. The formulation is based on the thermodynamic framework of irreversible processes in order to guaranty its physical consistency and to allow the opportunity to perform large scale computation at the structural case. Among the different choices allowed to model microcraking (anisotropic damage for example), a single scalar damage variable has been introduced in order to take into account of non linearities due to micro cracks effects, including the non symmetric response for tensile loading and compressive state of stresses. Based on strain decomposition in deviatoric and hydrostatic parts, the stiffness recovery is associated to the hydrostatic behaviour while frictional sliding is only concerned by the deviatoric one. The influence of sliding which occurs between the cracked surfaces has been considered in order to represent accurately hysteretic loops as well as the energy dissipation at the material scale. Related numerical aspects are presented ensuring convergence and robustness for structural casestudies. The integral form of non local models has been retained to avoid any spurious mesh dependency due to strain softening.

International audience

In the past few years, numerous methods for damage assessment for structural health monitoring were proposed in the literature. Several problems are raised for making these approaches practical for the engineer. The first concern is to determine whether a structure presents an abnormal behavior or not. Statistical inference is concerned with the implementation of algorithms that analyze the distribution of extracted features in an effort to make decisions on damage diagnosis. Learning algorithms have extensively been applied to classification and pattern recognition problems in the past years and deserve to be used for structural health monitoring. In addition, data acquisition campaigns of civil engineering structures can last from several minutes to years. Dealing with large amounts of data is not an easy task and suitable tools are required to correctly extract important features from them: symbolic data analysis (SDA) is such an approach. In this paper, some supervised learning methods (Bayesian decision trees, neural networks and support vector machines) are introduced to discriminate structural features and are developed within the concept of symbolic data analysis in order to compress data without losing its inherent variability. To highlight the different features of these techniques for structural health monitoring, this paper focuses attention on the monitoring of a railway bridge belonging to the high speed track between Paris and Lyon. During the month of June 2003, a strengthening procedure was carried out on this bridge. In so doing, vibration measurements were recorded under three different structural conditions: before, during strengthening. In the following years (2004, 2005 and 2006), new tests were performed to observe how the dynamic behavior of the bridge evolved, especially for the case of frequency changes. The objective was to verify whether the strengthening procedure was still effective or not, in other terms if the new data could be still assigned to the condition .after strengthening.. This paper reports the major results obtained and shows how the supervised learning techniques can be applied to cluster structural behaviors and classify new data. An original assignment approach is also presented: based on dissimilarity measures this approach shows that in fact the structural behavior of the bridge seems totally different of the initial behaviors used for training the supervised learning methods. Supervised learning algorithms

Most infrastructures are reinforced concrete (RC) structures. And these structures have to be kept operational. For that the stackholders have to watch and observe the noticeable signs of degradation resulting from interactions between the environment and their constitutive materials. Of course, these interactions can reveal cracks which are the major worry with respect to durability and sustainability. If no maintenance or repair actions occur this durability could decrease until the serviceability becomes affected and in some cases, until the structural safety is concerned. In this framework, the French national research programme CEOS.fr (Behaviour and assessment of special construction works concerning cracking and shrinkage) has been elaborated. Its aim is to show the behaviour evolution of special concrete structures particularly their cracking states (opening and space of cracks) and develop tools allowing the structural behaviour prediction (forecast). Associated with the project CEOS.fr, an international benchmark named Concrack (Control of cracking in RC structures) dealt with the modelling of the experimental behaviour of large specimens. In that context, the authors are focused on the modelling of one tested mock-up. It is a large reinforced concrete beam named RL1 subjected to a free shrinkage test followed to a bending test. The authors are concentrated on the mechanical part. In order to model the mechanical test, a 2D plane stress model for the bending beam is performed. In this case, both concrete models are used, Mazars one [Mazars, 1984] and Ricrag [Richard et al., 2010]. The steel model is a classical hardening elastoplastic law. The Ricrag model is a law based on the thermodynamics of irreversible processes coupling elasticity, isotropic damage and internal sliding. Thus, this model could show its capacities to predict the behaviour of the structure according to the experimental results. In this study, the authors show the effect of the boundary conditions on the numerical results and his importance to get a good accordance with the experimental results. Crack openings and spaces are obtained by post processing and compared with the experimental results and the global numerical results are also compared to the experimental ones. At last, the set of the results is encouraging.

The assessment of Coda Wave Interferometry (CWI) and Distributed Fiber Optics Sensing (DFOS) techniques for the detection of damages in a laboratory size reinforced concrete beam is presented in this paper. The sensitivity of these two novel techniques to micro cracks is discussed and compared to standard traditional sensors. Moreover, the capacity of a DFOS technique to localize cracks and quantify crack openings is also assessed. The results show that the implementation of CWI and DFOS techniques allow the detection of early subtle changes in reinforced concrete structures until crack formation. With their ability to quantify the crack opening, following early detection and localization, DFOS techniques can achieve more effective monitoring of reinforced concrete structures. Contrary to discrete sensors, CWI and DFOS techniques cover larger areas and thus provide more efficient infrastructures asset management and maintenance operations throughout the lifetime of the structure.