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In this study, scour-based vibrations of bridge piers are investigated using a bridge model in a water flume: first, the eigenmode corresponding to the measured frequencies of pier-like structures is identified. Secondly, the effect of the pier-deck interaction is studied. Finally, a theoretical model is proposed to characterize the pier vibration, and identify its input parameters.To this end, experimental campaigns were conducted and a laboratory scale model pier was tested in two configurations: single piers and two piers in bridge configuration. The experimental results enable the identification of the modal shape and indicate that the deck decreases significantly the pier's frequency. Parallely, a theoretical model was proposed to model the pier, where the soil was modeled with both lateral springs along the pier and a rotational spring at the base. These springs stiffness were then identified using a 3D-finite element model. These results, obtained with the theoretical and numerical models, are in good agreement with the experimental results with the bridge pier in the two tested configurations. Moreover the obtained theoretical, numerical and experimental results were compared to experimental data found in the literature, for further validation.

Non-linear finite element analyses have intrinsic model and user factors that influence the results of the analyses. However, non-linear finite element analysis can provide a tool to assess safety using realistic descriptions of material behaviour with actual material properties. A realistic estimation of the existing safety and capacity of slender column elements can be achieved by means of "true" material properties. Nevertheless, it seems that for some structural components, such as slender columns, non-linear finite element analyses can, due to its complexity and its various setting parameters, cause the risk of overestimating the real performance of analysed components or systems. Hence, an invited expert group has carried out an investigation into the experimental testing and the prediction of the bearing capacity of slender columns by performing independent non-linear finite element analyses in order to determine the practical applicability, and its inconsistencies, with respect to the stability failure of slender columns. This work aims the characterization of modelling uncertainties, concerning the prediction of slender columns stability when forecasted by non-linear finite element analysis., This paper was partly carried out during research exchanges at TU Brno (BUT), Lehigh University (LU). The authors acknowledge also the financial support provided by the SAFEBRIDGE ATCZ190 EU Interreg project, the Scientific Grant Agency of the Ministry of Education of Slovak Republic, the Slovak Academy of Sciences VEGA No. 1/0696/14, and Slovak Research and Development Agency under the contract No. APVV-150658. The computational results presented have been achieved [in part] using the Vienna Scientific Cluster (VSC).

External sulfate attack (ESA) and delayed ettringite formation (DEF) are well-known concrete degradation phenomena induced by ettringite crystallization. This paper proposes a poromechanical model based on the surface-controlled ettringite growth mechanism and the chemical composition of the solution, explaining both ESA and DEF in a similar model. The driving force for this expansion is the crystallization pressure from the supersaturation of the sulfate solution that leads to the formation of ettringite in pores. The growth of ettringite is separated into two processes: (1) the pore invasion process, where ettringite forms in the existing largest pores and then penetrates progressively into the ever-smaller capillary and gel pores, and (2) the deformation process during which damage and cracks occur. Two kinetic constants corresponding to these two processes are proposed in this paper, and the predicted expansions show good consistency with the experimental measurements found in the literature.

The present work analyses the basic creep of concrete compositions for which 75% of Portland cement is substituted by limestone filler and/or blast furnace slag. Compressive creep tests are performed during and after the peak of hydration of the slag in order to track the effect of the slag on the development of the creep properties. An adapted version of the Model Code 2010 (MC2010) is used to model basic creep. It is observed that the high substitution rate of cement by limestone filler and/or slag leads to a significant change in the evolution of the viscoelastic properties of concrete till a significant degree of reaction of slag is reached. It corresponds to the end of the second peak of hydration due to slag. After the slag peak of hydration, the basic creep is similar to ordinary Portland cement concrete with equivalent water-to-binder ratio. For very early age, a new model is developed and is composed of two terms which consider the hydration of (i) Portland cement and (ii) slag in the aging of the specific creep function.

ICTAEM 2020, Proceedings of the Third International Conference on Theoretical, Applied and Experimental Mechanics , Athenes, GRECE, 14-/06/2020 - 17/06/2020; The paper presents an experimental test of macrocrack propagation in bones associated with a numerical strategy to determine from this test some mechanical properties by inverse identification. A 3 point bending test is performed on a notched segment of long human bone, and the load vs notch opening displacement is measured. The compliance method is applied in the context of a realistic FE simulation of the test. A first application of this methodology is described and shows its feasibility and capabilities. The ultimate objective of this research project is to develop a probabilistic modelling of the macrocracking processes in human long bone tissues based on an experimental database of mechanical parameters fed up by this methodology.

The prediction of delayed strains is very important in prestressed concrete structures. Temperature and relative humidity of concrete structures are two important parameters for this prediction and, on site, are varying over time. Based on model code 2010 and superposition principle, we propose an analytical method to take into account these varying temperature and relative humidity. The coupling between delayed strain of concrete and relaxation of stress in prestressing bars are also considered. We validate the proposed method against in-situ measurement on the mockup of VeRCoRs which is a 1/3 scale mockup of a biaxially prestressed confining building. In the end, we discuss the importance of taking into account the coupling between delayed strain and relaxation of stress, the influence of varying temperature on delayed strain of concrete and also the value of Poisson's ratio of drying creep.

IABSE Symposium, Towards a Resilient Built Environment - Risk and Asset Management, Guimaraes, PORTUGAL, 27-/03/2019 - 29/03/2019; Modern design codes recommend to ensure an appropriate level of robustness to prevent from disproportionate collapse under an exceptional event. One of the major difficulties is to quantify the concept of structural robustness when checking the structural integrity under exceptional situations. This study proposes practical means for assessing structural robustness, by identifying the maximum capacity of the structure to withstand significant structural failure scenarios. Each scenario is characterized by the required energy of events to cause the local failure. Two structural robustness indicators are then introduced: a first index identifies the maximum capacity of the structure to resist a local failure, and a second one identifies the maximum degree of failure propagation.

Each year hydraulic structures such as levees and earth dams are hit by disorders that can lead to their collapse. A dike reinforcement method such as the deep soil mixing gets interest for its reinforcement capacity at moderate cost. We report on the use of a non-destructive technique to effectively assess the proper achievement of these structures and their evolution in time. More particularly, 2D-electrical resistivity imaging (2D-ERI) was used to assess a cut-off wall. We evaluate the benefits and limitations of three acquisition techniques (longitudinal, transversal and cross-hole). To complete the interpretation, we performed a comprehensive geotechnical study to make a diagnosis of the structure. Each inversion result is combined with numerical modelling that enlightens limitations of the acquisition techniques and improve the interpretation. Results show that 2D-ERI can present a real benefit for the assessment of cut-off walls even if the dimensions of the cut-off wall limit the detectability of deep heterogeneities.

This paper presents an analysis of the influence of the umbrella arch on the settlements induced by shallow tunneling, based on three-dimensional finite element simulations using CESAR-LCPC. The approach takes into account the actual geometry of the umbrella arch and the lining, and the various aspects of staged construction, notably the cycle of installation of the pipes. The results show that the influence of the umbrella arch on the settlements remains modest, at least for the range of parameters adopted in this study. Also, the results show that the numerical analysis can be carried out with a simplified geometry.

The use of reclaimed asphalt pavement (RAP) in asphalt mixtures is considered as one of the best sustainable practices in the construction of transportation infrastructures. Extensive efforts have been made to design, produce, and evaluate RAP mixtures produced by the hot recycling technology in asphalt plants. However, the inconsistencies or contradictive conclusions regarding the performance of RAP mixtures reported in the literature impede the use of high percentage of RAP in asphalt mixtures. One of the knowledge gaps for the discrepant behaviors of RAP mixtures is the negligence of the influence of production thermal processes, e.g. mixing time, production temperature, silo storage temperature and time, etc., on the mechanical performance of RAP mixtures. In this context, this paper synthetically reviewed the fundamental thermodynamics and kinematics involved in the plant production of RAP mixtures and the corresponding numerical methodologies to quantify the thermal processes. Three prevailing numerical methods, including overall energy balance method, 1-D thermal-granular model, and coupled computational fluid dynamics and discrete element method, are used to quantify the temperatures of hot gases, virgin aggregates, and RAP particles in the drum dryer. Then, the key production parameters that could influence the performance of RAP mixtures were identified based on the experimental studies. The review results from the experimental studies highlighted the importance of mixing time, mixture discharge temperature, and silo storage time on the mechanical performances of laboratory-produced and plant-produced RAP mixtures. The review findings from this study can be used to guide the best practice of the production of RAP mixtures and further contribute to the energy saving and sustainable construction of using RAP in asphalt mixtures.

The determination of the thermal resistance of a building envelope is fundamental for the evaluation of the thermal performance of buildings. This could help to evaluate and verify the energy efficiency performance of constructions before renovation, during construction, upon delivery and during use. Some methods exist in the scientific literature but they do not allow a systematic, accurate and rapid evaluation. This paper presents a numerical benchmark of identification methods used to estimate the thermal resistance of an opaque wall. The robustness of each identification technique is investigated in terms of bias and uncertainties. The proposed estimation approach is based on an active method, in which the structure is heated in order to create a temperature gradient across the wall, and on the analysis in dynamic regime of the thermal response of the wall. The investigated walls are internal wall insulation (IWI) and single-wall structures (SWS). The results of the numerical study show that RC model-based identification techniques are the most suitable to estimate the thermal resistance of IWI at a very low computational cost. Nevertheless, the modelling error being larger for the SWS than for the IWI, 1D transient heat equations should be preferred for the identification of SWS thermal resistance. The active thermal strategy allows a relevant estimation of the thermal resistance with an observation time of less than 24 h.

A ~1000 m3 rockslide occurred close to Lorca (SE Spain) during the main shock (Mw = 5.1) of the May 2011 seismic sequence. The location of the rockslide, within 10 km of the earthquake epicenter and along the southern slope of a valley in which similar geological conditions occur on both slopes of the valley, suggests a significant near-field effect due to local seismic response. This could be related to the specific interaction between the topography and the obliquely propagating seismic waves. A dynamic stress strain numerical model was constructed using the FLAC 7.0 finite difference code to back analyze the Lorca rockslide event and relate its occurrence to both the local seismic amplification and the interaction between seismic waves and local topography. The results indicate that only for seismic waves with incidence angles in the range 0°–50° are the occurred slope instabilities expected. These results do not significantly change when varying the values for either stiffness or strength parameters within the range of the experimental data., This work was partially funded by research groups VIGROB-53 and VIGROB-184 (Universidad de Alicante) and by the projects tec2008–06764–c02–02 and CGL2011–30153–c02–02.

Delayed Ettringite Formation (DEF) in concrete is likely to develop in massive civil engineering structures such as bridges, nuclear plants, and dams with major security issues. DEF pathology can lead to swelling and cracking which may significantly impact mass transfer and mechanical properties. It is then of major importance to build predictive tools for engineering conceptions and expertizes. In this contribution,the chemical swelling evolution is integrated within the overall constitutive law of concrete that, besides, can experience other phenomena such like damage, plasticity, and long term creep, not all considered here. On another hand, as DEF is activated by environmental humidity above a certain threshold, we use a notion of effective time that takes into account the cumulative exposition above this threshold. Hence, a special care is taken with regards to the chemical irreversibility, together with the humidity-drying cycles. The computationsare used to calibrate the model parameters with the help of results from an experimental compaign where two kinds of concretes were studied; one with siliceous aggregates, and one with calcious aggregates. We show the efficiency of the developed numerical tool through a series of examples., La pathologie de Réaction Sulfatique Interne (RSI) se développe dans les structures massives telles que les ponts, barrages, radiers d'installations nucléaires. Elle peut induire des gonflements significatifs qui peuvent influencer les propriétés mécaniques. Il est donc important de développer des outils prédictifs afin de mener des expertises. Dans cette contribution, on s'intéresse à la prise en compte de conditions d'humidité variables dans la cinétique de gonflement. Les exemples numériques permettent également de calibrer les paramètres des modèles pour mener des calculs d'ouvrages. Ici deux types de bétons sont testés: l'un basé sur des granulats à base de silice, l'autre sur des granulats à base de calcaire. On montre l'efficacité de l'outil numérique par la méthode des éléments finis développé à cet effet.

EURO-C 2018 - Computationnal Modelling of Concrete and Concrete Structures, BAD HOFGASTEIN, AUTRICHE, 26-/02/2018 - 01/03/2018; Internal swelling reactions (ISR) can affect long term duration of reinforced concrete (RC) structures by causing cracking and expansion of concrete material. These pathologies mainly consist in Alkali Aggregate Reaction (AAR) and/or Delayed Ettringite Formation (DEF). Thus, it is necessary to provide robust predictive numerical models able to re-assess the mechanical state of affected structures. A new numerical strategy is proposed in this paper to compute the evolution of the ISR reaction from intrinsic parameters to be identified for the reactive concrete. Based on Larive's model, evolution of the chemical strain is written in order to assume the irreversibility of the mechanisms and to take into account time history of the Relative Humidity and Temperature supported by the concrete specimen. An effective time is proposed to store history of the reactive concrete and to be able to compute evolution of the chemical strain.

Concrete digital fabrication is an innovative construction approach where infrastructural elements can be built additively without using formwork. This represents a significant advantage, but also introduces materials engineering challenges, as the requirements normally fulfilled by the formwork are now imposed on the concrete. In this paper, it is discussed how admixtures can be employed to achieve the rheological and hydration properties necessary for printable concrete. An overview of various admixtures currently implemented in standard practice is presented. Then, the main required concrete states for extrusion and deposition processes are analyzed with respect to required performances and potential admixtures. Finally, possible side effects and incompatibilities are discussed, as well as how they could be unconventionally used for printable concrete purposes. The main objective is to demonstrate how admixtures will be critical in the development of concrete systems to realize digital fabrication, and to ultimately motivate investigation in the key areas discussed.

This paper presents design of a self-stabilizing retaining diaphragm wall, using conventional analytical calculation method based on subgrade reaction coefficient and by numerical method with finite elements method FEM can lead to various uncertainties. Hence, engineers have to calibrate a computational strategy to minimize these uncertainties due to numerical modeling. For both two methods, this paper presents various simulations with the structure installed into the supported ground without surcharge. For the first method, the analysis has investigate the influence of main factors such as the wall rigidity, the different stages of excavation, the Young’s modulus, the cohesion and internal friction’s angle of the soil. For the FEM method, two constitutive soil models are used such as Mohr-Coulomb MC and hardening soil model HSM. In case of the last model HSM, the variation of required and additional factors for the model was investigated as well as secant modulus stiffness Eref50, unloading and reloading stiffness modulus Eur, power factor m and Over-consolidated ratio OCR. The results from of the various simulations carried out are confronted with other experimental and numerical results [4]. Avery good coherence results are showed.

International audience; The paper addresses the response of a semi-rigid rockfall protection barrier using numerical models. The study show a large dependence of the barrier response to the impact conditions. The block size and impact position, rather than the velocity direction and magnitude induce different modes of failure of the fence, which in turn result in different values of failure energy. As a result, the barrier capacity cannot be established in a deterministic way. The effectiveness of structures as such can be more successfully evaluated through a reliability probabilistic approach. Results can be used to create a meta-model of the barrier response which can be incorporated into rockfall simulation models, enabling a reliable and comprehensive design of rockfall mitigation interventions performed with this type of structure.

Structural health monitoring (SHM) relies on data acquired from sensorial systems installed on site, and is nowadays being used more often not only for asset management, but also in critical structures when there is the need to detect damage in an early stage, before it impairs structural performance and safety. Early detection of damage in critical structures relies on the acquisition of continuous streams of information and on reliable techniques capable of analyzing it in real time, without generating false alerts. In this context, the combination of data fusion strategies, capable of converting large amounts of data into small pieces of information, with pattern recognition algorithms, which are able to analyze this information in real time, is addressed in the present paper with the objective of developing an original strategy capable of (1) removing the effects of regular actions imposed to structures without the need to measure them and of (2) compressing entire SHM data sets of arbitrary dimensions into a sensitive single-valued damage index. These capabilities are achieved by combining principal component analysis, the broke-stick rule, clustering methods, symbolic data objects, and symbolic distances. The proposed strategy was tested and validated with a numerical model of a cable-stayed bridge, using experimental data as input. From this analysis it was observed that, under the noise levels measured on site, the proposed strategy is able to automatically detect damage as small as 1% of stiffness reduction in a single stay cable. This sensitivity evidenced by the proposed strategy can be considered particularly high because it was obtained from a small amount of inexpensive sensors with a static character and because it was associated with a false detection incidence of only 0.1%.

This paper presents the appraisal of structures affected by the alkali–aggregate reaction (AAR) and is based on the overall philosophy and principles that have already been established in a Rilem report to be published. This report is part 2 of the recommendations on diagnosis and appraisal that have been developed in the frame of the Rilem technical committee 219-ACS. It recommends that, from the start of an investigation, there should be close links between the materials science team inspecting and testing for diagnosis and the structural engineers carrying out an appraisal. This paper first describes the initial appraisal that is based on site investigations (cracking index, global deformation and environment analysis) and the laboratory investigations on the cores taken from the structure (mechanical testing, residual expansion tests) in order to obtain a severity assessment of the structure. Then it presents the structural assessment that includes the severity rating of the structural elements and the structural assessment based on a numerical modelling referring to Larive's law.

T; This study is focused on evaluating local response and the earthquake-induced strains in a highly heterogeneous alluvial valley through numerical modelling approach. The case study is located S of Rome, in correspondence to the Fosso di Vallerano alluvial valley. A high-resolution engineering-geological model of the alluvial deposits that fill the valley was derived by field investigations. Several tens of borehole log-stratigraphies were also taken into account. Outputs of 1D and 2D numerical models were analysed in terms of maximum shear strain (MSS) and Shear Strain Concentration Index (SSCI) to highlight where shear strain concentrates in the engineering-geological model as well as role of lateral heterogeneities in the distribution of shear strain within the alluvial deposits. The here reported preliminary results show that earthquakeinduced strain effects: i) can be mainly referred to 2D conditions, ii) are mainly influenced by the heterogeneity of the alluvial deposits, iii) are poorly influenced by the shape of the bedrock.

In order to define and quantify the rhythm and amplitude of the processes of erosion and sedimentation on broad tidal flats, in situ measurements of sediment elevation have been performed in the western part of the Mont-Saint-Michel bay. The amplitude of reworking is generally low (< ± 5 cm), and variable from west to east. The wind influence on tidal currents and surficial reworking emphasizes erosion phases rapidly followed by accretion of similar amplitude on the whole tidal flat. A numerical model for hydrodynamics and sediment transport is applied to Mont Saint Michel Bay, where ecological concerns are related to sediment transfers., Les rythmes et l'ampleur des processus « érosion-sédimentation » ont été suivis, à trois échelles de temps, sur le vaste estran sablo-vaseux de la partie occidentale de la baie du Mont-Saint-Michel. Les mesures in situ du niveau de l'interface eau-sédiment montrent que l'amplitude générale des remaniements est généralement inférieure à 5 cm et variable d'ouest en est. L'influence du vent sur les remaniements superficiels souligne des phases d'érosion rapidement suivies par des phases de sédimentation de même amplitude sur l'ensemble de l'estran. Un modèle numérique hydro-sédimentaire, validé par des mesures sur l'estran, permet de simuler les courants et les transferts de sédiments en zone intertidale.

In this paper, an improvement to the probabilistic discrete cracking model of fibre reinforced concretes, developed in the past by Pierre Rossi, is proposed. In this new model: – Cracks creation and propagation in the concrete are taken into account by using special interface elements. These interface elements open when the normal tensile stress at their centre of gravity reaches a critical value. The probabilistic aspect of the cracking process is given by the fact that the critical value of the tensile stress is randomly distributed through the mesh elements. – Immediately after the creation of cracks, the fibres bridging effect is then taken into account in a damage model approach. The probabilistic aspect consists of randomly distributing the post-cracking energy. The improved numerical model is used to analyze the shear behaviour of a steel fibre reinforced concrete beam. The numerical simulations are compared with the experimental results in terms of the beam’s global behaviour and the cracking process (number of cracks, spacing and opening). The numerical and experimental results agree well.

The prediction of settlements caused by shallow tunnelling is mainly based on two-dimensional modelling with the stress relaxation method. In this article, we illustrate some limits of this method. We define a characteristic tunnel typical for the Paris region, then we adjust the relaxation factor of a 2D model to have the same maximum settlement as in the equivalent 3D model. Once this fitting is done, we look at the stress invariants paths. The evolution of the deviatoric stress above the tunnel crown, before the setting of the lining, is opposed according to the considered simulation. This result explains why the stress relaxation factor depends strongly on the constitutive model. Furthermore, it shows that the use of a 2D model for a stress analysis of the soil is uncertain. The discussion is illustrated by simulations carried out with three different constitutive models: a perfect elasto-plastic, a non-linear elastic and the Hardening Soil Model.; La prévision des tassements provoqués en surface par le creusement de tunnels peu profonds repose largement sur le recours à des modèles numériques bidimensionnels, en s'appuyant sur la méthode convergence-confinement. Dans cet article, on cherche à mettre en évidence les limites de cette approche. On définit une situation caractéristique du creusement d'un tunnel en région parisienne, et on cale le taux de déconfinement d'un modèle bidimensionnel afin d'obtenir le même tassement maximal que pour le modèle tridimensionnel équivalent. Une fois ce calage effectué, on s'intéresse au profil des invariants de contraintes. L'évolution de la contrainte déviatorique au-dessus de la voûte du tunnel, avant la mise en place du soutènement, est opposée selon la modélisation. Ce résultat explique pourquoi le taux de déconfinement dépend fortement de la loi de comportement et ne peut être estimé a priori dans le cas de lois de comportement avancées. L'illustration avec trois lois de comportement différentes, une loi élasto-plastique parfaite, une loi élastique non linéaire et le Hardening Soil Model met en évidence les limites très significatives de la modélisation bidimensionnelle de tunnels pour la prévision des tassements.

International audience; In this paper, local structure of bare soil is analyzed from the fractal point of view. Soil surface profiles were created from three dimensional (3-D) stereoscopic images of soil surface leading to 3-D numerical reconstruction of the soil topography with very fine resolution. Investigations are done with a database (four soils) that includes three main soil classes according to the way of tillage: smoothed field from rainfalls, ploughed, and sowed fields. The fractional Brownian model developed by Mandelbrot is used to describe local structure of soil roughness. For the database soils, fractal nature of the profiles is demonstrated over a finite range of scales showing a good stability of fractal dimension for each one. This model also provides an excellent analytic fit to the experimental correlation function of soil. Therefore, a new method to calculate its shape at the origin and a more stable correlation length is presented. To study the influence of the band-limited fractal nature of the soil on radar signal, the Moment Method is used to evaluate the backscattered field and to obtain the radar cross-section by statistical averaging. Surfaces used for this electromagnetic simulation are cylindrical and perfectly conducting. A method is developed to generate soil surface profiles that have the same statistical properties and the same roughness parameters values (rms height, correlation length, and fractal dimension) as what has been found on our database soils. The generation method is based on an initially Gaussian correlated random profile, modified by the random midpoint displacement method to introduce the short-range disorder that depends on fractal dimension. The radar signal level computed on these surfaces by the Moment Method shows the dependence of backscattering on fractal dimension and new aspects in electromagnetic scattering behavior over soils.

International audience; In this paper, a new approach for soil roughness description is proposed. It is based on numerical three-dimensional soil surface images obtained by a stereoscopic device with a very fine resolution. The collected database contains four soils with different roughness (from smooth to ploughed). Each three-dimensional (3D) image is first approximated by juxtaposition of small plane facets. Statistics are then retrieved from sizes and slopes of facets in the segmented image. Analytical formulations are proposed for statistical laws showing a clear discrimination between the different soils of our database. In order to study numerically backscattering behaviour over soil, we generate profiles with respect to the retrieved statistics by applying Monte Carlo method. The Moment Method is used to compute the backscattered field over perfect conductor generated profiles. Finally, the results of numerical electromagnetic simulation are compared with the analytical Integral Equation Model (IEM) solution. Excellent agreement is obtained for soils belonging to the validity domain of IEM. For rougher soils, our model shows a realistic behaviour with incidence angle.

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%.

The interaction of seismic waves with slopes is a major factor influencing landslide movements that involve slope stability, local site seismic amplification and topographic effects affecting ground motion. The results of a numerical study of landslide movements induced by the interaction of seismic waves with step-like slopes are presented here. To investigate this input–slope interaction, a dynamic analysis was performed using the finite difference stress-strain numerical code FLAC 6.0 under visco-plastic conditions. The dynamic signals were selected to be representative of different peak ground accelerations (PGAs), Arias intensities and frequency contents, and they were used in a parametric study of different step-like slopes with different geometrical configurations in terms of dip, height and thickness of geological strata. The derived outputs were processed for a seismic amplification analysis and to evaluate the induced stress-strain effects in terms of progressive failure and resulting displacements. The obtained results: i) describe a fundamental role of topography in amplifying or de-amplifying the seismic ground motion; ii) demonstrate that the progressive failure of unsheared slopes influences the seismic amplification; iii) show that the strain effects on unsheared slopes, in terms of progressive failure, are more intense with increasing Arias intensity and slope dip; iv) prove that amplification or de-amplification processes can justify the values of displacements involving pre-existing landslide masses, which are significantly different with respect to those expected on the basis of sliding block approaches (i.e., Newmark's and flexible sliding block methods); v) highlight that, in the geological setting considered here, the seismically induced displacements arising from the reactivation of pre-existing landslide masses can be significantly underestimated by sliding block approaches in the case of low-angle slopes characterised by high K values, i.e. the ratios between the critical pseudostatic threshold (ky) of the landslide and PGAs of the applied seismic input.

IFSTTAR has developed a Multi-Scale Cement Based Composite (MSCC). This composite material is strain hardening in tension and exhibits ultra-high strengths as well in both compression and tension. The main research objectives for the present paper are the determination of the strain hardening properties of the material: using a newly developed tensile test in conjunction with a finite-element-based inverse analysis, the input parameters of an (adapted) numerical model can be identified. Therefore, numerical simulations can be performed to describe the bending behaviour of a thin slab having a thickness representative of the corresponding industrial application. The main conclusions of this study are: – The studied material clearly exhibits strain hardening in tension with a uniaxial tensile strength of about 20 MPa and a modulus of rupture of about 50 MPa. – Elasto-plastic behaviour with strain hardening is a relevant mechanical model (for the studied material) for designing (by the finite element method) structural elements behaving principally in bending.

This paper is focused on the probabilistic updating of the local parameters of a structural model by Bayesian networks. The approach uses their inference property to update the probability function parameters (mean and standard deviation) related to the variables from the measurements of the structural response given by load tests. To make satisfying the computational effort, the choice of the number of random variables is discussed and relies on several sensitivity indicators given by a structural reliability analysis. The study of a prestressed beam highlights the different corpus required for applying this updating approach: the different structural mechanics theories for providing a pertinent mechanical model, the reliability theory to analyze the sensitivity of the different variables, the Bayesian network theory to update the a priori probability functions of the input variables. The comparison with the experimental data shows that the relative error between the average experimental and numerical response can be significantly reduced with the help of the proposed updating process.

The mechanical response of earth structures reinforced with steel strips to loads associated with rail traffic is not well known. In order to better understand the deformations induced by train loads, and to improve design methods, a full-scale structure was built, instrumented, and tested near Rouen, France. Finite-element analyses were performed both in plane-strain and three-dimensional conditions, using different approaches to account for the interaction between the strips and the backfill material. After calibration of the soil-strip interface parameters for a load of 90 kN, simulations of the wall response to a load of 850 kN provided results in good agreement with measurements. Numerical models showed that the soil-strip interface parameters have a major influence on the predicted behavior. The proposed approach could be used for further studies of the influence of geometric and mechanical parameters.

For managing highway bridges, stakeholders require efficient and practical decision making techniques. In a context of limited bridge management budget, it is crucial to determine the most effective breakdown of financial resources over the different structures of a bridge network. Bridge management systems (BMSs) have been developed for such a purpose. However, they generally rely on an individual approach. The influence of the position of bridges in the transportation network, the consequences of inadequate service for the network users, due to maintenance actions or bridge failure, are not taken into consideration. Therefore, maintenance strategies obtained with current BMSs do not necessarily lead to an optimal level of service (LOS) of the bridge network for the users of the transportation network. Besides, the assessment of the structural performance of highway bridges usually requires the access to the geometrical and mechanical properties of its components. Such information might not be available for all structures in a bridge network for which managers try to schedule and prioritize maintenance strategies. On the contrary, visual inspections are performed regularly and information is generally available for all structures of the bridge network. The objective of this paper is threefold (i) propose an advanced network-level bridge management system considering the position of each bridge in the transportation network, (ii) use information obtained at visual inspections to assess the performance of bridges, and (iii) compare optimal maintenance strategies, obtained with a genetic algorithm, when considering interests of users and bridge owner either separately as conflicting criteria, or simultaneously as a common interest for the whole community. In each case, safety and serviceability aspects are taken into account in the model when determining optimal strategies. The theoretical and numerical developments are applied on a French bridge network.

This paper examines the possibility of applying a homogenization procedure to analyze the convergence of a tunnel reinforced by bolts, regarded as periodically distributed linear inclusions. Owing to the fact that a classical homogenization method fails to account for the interactions prevailing between the bolts and the surrounding ground and thus tends to significantly overestimate the reinforcement effect in terms of convergence reduction, a so-called multiphase model is presented and developed, aimed at improving the classical homogenization method. Indeed, according to this model, the bolt-reinforced ground is represented at the macroscopic scale as the superposition of two mutually interacting continuous phases, describing the ground and the reinforcement network, respectively. It is shown that such a multiphase approach can be interpreted as an extension of the homogenization procedure, thus making it possible to capture the ground–reinforcement interaction in a proper way, provided the constitutive parameters of the model and notably those relating to the interaction law can be identified from the reinforced ground characteristics. The numerical implementation of this model in a finite element method-based computer code is then carried out, and a first illustrative application is finally presented. Copyright © 2008 John Wiley & Sons, Ltd.

A numerical model has been developed to predict early-age cracking for massive concrete structures. Taking into account creep at early-age is essential if one wants to predict quantitatively the induced stresses if autogenous or thermal strains are restrained. Because creep strains may relax internal stresses, a creep model which includes the effects of hydration and temperature is used. For the prediction of cracking, a simple elastic damage model is used. Numerical simulations are performed in order to predict the behaviour of a massive wall and a concrete containment of a nuclear power plant. They show that significant relaxation of stresses (due to creep) occurs only after about 10 days, after cracking occurs. Moreover, since temperature in concrete may reach important values in massive concrete structures, it appears that effect of temperature on creep must be taken into account for an accurate prediction of cracking.

Spring frost may strongly affect fruit production in the Central Valley of Chile. Minimum temperatures are spatially variable owing to topography and soil conditions. A methodology for forecasting minimum temperature at a regional scale in the Central Valley of Chile, integrating spatial variability of temperature under radiative frost conditions, has been developed. It uses simultaneously a model for forecasting minimum temperatures at a reference station using air temperature and humidity measured at 6 pm, and topoclimatic models, based on satellite infra-red imagery (NOAA/AVHRR) and a digital elevation model, to extend the prediction at a regional scale. The methodological developments were integrated in a geographic information system for georeferencing of a meteorological station with satellite imagery and modeled output. This approach proved to be a useful tool for short range (12 h) minimum temperature prediction by generating thermal images over the Central Valley of Chile. It may also be used as a tool for frost risk assessment, in order to adapt production to local climatological conditions., Les gelées de printemps sont un facteur limitant important pour l’arboriculture chilienne dans la vallée centrale du Chili. Les températures minimales présentent une forte variabilité, en raison de la topographie et de l’occupation du sol. Cette étude présente une méthode de prévision des températures minimales à l’échelle régionale, intégrant la variabilité spatiale des températures en conditions de gelées de printemps. Elle utilise à la fois un modèle local de prévision de la température minimale utilisant la température et l’humidité de l’air mesurées sur une station météorologique à 18 h TU, et un modèle topoclimatique basé sur l’utilisation de thermographies infrarouge (satellite NOAA/AVHRR) et d’un modèle numérique de terrain, pour étendre la prévision à l’échelle régionale. Ces modèles ont été intégrés dans un système d’information géographique pour la géoréférenciation des stations météorologiques de référence par rapport aux images satellitaires, et les sorties du modèle. Cette approche permet de générer des images de températures minimales prédites avec 12 h d’avance, sur l’ensemble de la vallée centrale du Chili, avec une précision voisine du degré Celsius. Elle permet également de faire un zonage des risques de gel pour une meilleure adaptation des cultures aux conditions climatiques locales.

The potentials and limits of estimating canopy parameters are investigated using only a reflectance spectrum in the optical domain, and the PROSPECT + SAIL model. Simulations are performed on A VIRIS (Airborne Visible~Infrared Imaging Spectrometer) equivalent spectra, corrected for the atmospheric effects. It is established that this model is numerically invertible. The sensitivity analysis of reflectance spectral features to changes in the values of canopy parameters (leaf mesophyll structure N, chlorophyll a + b concentration Cab, water depth Cw, leaf area index, LAL and average leaf inclination angle 01) suggests that the accuracy of the inversion procedure needs some constraints. The C~a, and Cw parameters, which describe the leaf physiological status, can be generally retrieved with a reasonable accuracy; it is somewhat di3ficult to estimate the canopy geometrical parameters (LAI and 01) separately. Determining the fraction of absorbed photosynthetic active radiation (APAR) with parameters derived from the inversion procedure is discussed.