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In order to avoid environmental pollution by effluents, the incorporation of electrical conductive yarns in a waterproof membrane allows detecting a leak or crack on industrial concrete structure. The membrane is made of composite materials: a glass textile structure equipped with the detector yarns and molded in an epoxy resin. The liquid’s detection and the data’s transmission depend on the yarn’s conductivity variation and its chemical and physical properties. This study aims to develop a water detector monofilament from conductive polymer composites (CPC): an immiscible polymers blend (polyamide 6.6/elastomer) filled with carbon nanotubes (CNT). The addition of elastomer in the CPC yarn is important to withstand the mechanical deformation of the resin structure without breaking. The morphology of the immiscible polymers blend and the localization of the CNT influence the electrical conductivity of the yarn and thus, its property of water detection. Two principles of water detection are investigated with this blend: the short circuit and the absorption. For the short circuit, the presence of liquid is detected when the liquid creates a conductive path between two yarns in parallel. While, the absorption principle is based on the conductivity variation with the yarn’s swelling in contact with water.

We use two different purely empirical approaches to estimate the non-linear transfer function between a reference rock and a sedimentary site from recordings of weak ground motions and site-condition proxies. The modulus of the linear transfer function is first computed from weak motions and then modulated with a correction to consider non-linear soil behavior. Afterward, a time delay between the rock and site stations is considered using the weak motions delays and a minimum-phase assumption is used to derive a complex transfer function, which then allows to recover the prediction of acceleration time series a(t) at the sedimentary site. We apply these two approaches to the material provided for step 3 of the blind prediction exercise organized by the ESG6 Conference. The predictions were compared to the recordings that were provided after the blind test and to the overall predictions performed in the benchmark. Both methods underestimate the non-linear effects on the site response. For the foreshock, it contributes to improve the prediction compared to the other predictions. However, the prediction is less accurate for the mainshock. The prediction is also based on the average linear transfer function which, in case of large variability between weak motion transfer functions, may underestimate at some frequencies the amplification. Both of these purely empirical methods provide an honorable prediction of the Fourier spectra and acceleration time histories of the two target events, as the methods required only recordings of weak motions at the target and a referent sites and very simple description of the soil profile. The use of moderate motions to constrain the frequency shift prediction for the second method and the consideration of an alternative phase modification are possible ways to improvement.

By incorporating electrically conductive yarns into a waterproof membrane, one can detect epoxy resin cracking or liquid leakage. Therefore, this study examined the electrical conductivity variations of several yarns (metallic or carbon-based) for cracking and water detection. The first observations concerned the detectors&rsquo, feasibility by investigating their conductivity variations during both their resin implementation processes and their resin cracking. Throughout this experiment, two phenomena were detected: the compression and the separation of the fibres by the resin. In addition, the resin cracking had an important role in decreasing the yarns&rsquo, conductivity. The second part of this study concerned water detection. Two principles were established and implemented, first with yarns and then with yarns incorporated into the resin. First, the principle of absorption was based on the conductivity variation with the yarns&rsquo, swelling after contact with water. A short circuit was established by the creation of a conductive path when a drop of water was deposited between two conductive, parallel yarns. Through the influence of the yarns&rsquo, properties, this study explored the metallic yarns&rsquo, capacity to better detect water with a short circuit and the ability of the carbon-based yarns to detect water by the principle of absorption.

In this study, we compute site amplification estimates and response spectral ratios for different acceleration time histories scaled to different PGA's by propagating them through 1D soil models with stochastic variation of their mechanical properties. We use three models of wave propagation: the widely known equivalent linear model (EQL) (Schnabel et al., 1972), the frequency-dependent equivalent linear model (AKEQL) (Kausel and Assimaki, 2002), and the elastoplastic nonlinear model (NL) developed by Iwan (1967). We have selected four sites from the French permanent accelerometer network (RAP) deployed in the city of Nice, which is characterized by local strong site amplification due to alluvial filling. A sensitivity study on the numerical methods shows that purely nonlinear analysis greatly depends on the input motion whatever the rock input PGA (PGAr) is; whereas equivalent linear analyses have less dependency with respect to PGAr. We present then the variability of amplification estimates among the wave propagation models. We found that frequency-dependent equivalent linear results are close to those from the traditional equivalent linear model for PGA's larger than 0.7g. Conversely, for intermediate PGAr values, the first model de-amplifies the high frequencies much lower than the second one. Furthermore, the standard deviation of amplification estimates increases as PGA and frequency increase regardless of the utilized wave propagation model. Using the previous results, the response spectral ratio as a function of PGAr has been computed and inserted in simplified site-specific probabilistic seismic hazard assessment (Cramer, 2003). Finally, a comparison with experimental data shows that 1D modeling is a first order approximation of site effects in Nice.

For several years, the problematic about soil-structure interaction (SSI) have been studied in order to refine the evaluation of the seismic risk at local scale. This thesis particularly focuses on the quantification of the effects induced by the presence of buildings on the local seismic hazard in a sedimentary valley and on the characterization of dynamic parameters sensitive to soil-structure interaction from experimental ambient vibration data and 3D numerical models.Developed within the framework of the Ritmica project supported by the IDEX JEDI of the University Côte d’Azur, the objective of this thesis is to assess the respective impact of the site stratigraphy, of the geology and of the building on the seismic hazard. To do this, one of the highest seismic risk area in France mainland is chosen as study case: the lower Var valley. Many experiments have been carried out there for several years, including instrumentation of buildings, engineering structures and free field sites which have made it possible to define and describe the geological configuration of the valley and the dynamic behavior of some of the surrounding structures.In the aim of better characterize the seismic hazard in the Var valley taking into account the presence of existing buildings, multiple campaigns of ambient vibration measurements were performed on the basin and on the rock of the valley and also, at the level and inside the highest buildings in the valley. These data allow first, to define the 3D geotechnical model of the valley from available geotechnical and geophysical data and second, to calibrate simplified numerical model of building in order to establish a 3D finite element model of the valley including building at the top. This model is used to numerically simulate the seismic wave propagation in the Var valley using simulated earthquake. The soil model of the valley permits to better delimit the basin-bedrock interface and the seismic wave velocities that constitute important elements in the study of site effect. This model shows that the basin thickness increases from North to South from 50 m deep to more than 100 m under the Nice airport with average Vs velocity around 400 m.s-1. A numerical study done on five finite element models of building (4 low-rise and one high-rise, reinforced concrete and masonry) shows that bending type buildings are the most prone to SSI and that stiffness horizontal irregularities play a major role in SSI. The instrumentation campaigns of buildings in the Var valley allow to get a large set of data for the identification of the dynamic behavior of buildings, the study of SSI and the characterization of the spatial variability of the ground motion. These dense instrumentation campaigns allow to check that the first mode shape of building, thereafter used in the calibration of simplified model through simple relationship, corresponds to a bending mode. The analysis of the rocking spectral ratio and of random decrement functions is useful for the characterization of SSI from vertical temporal series at the base of buildings. To study the influence of lithological site effect and buildings on the surface ground motion, seismic wave propagation has been numerically simulated in five different 3D finite element site-city models characterized using ambient vibration recordings and including various city configurations., Depuis plusieurs années, les problématiques portant sur l’interaction sol-structure (ISS) sont étudiées afin d’affiner l’évaluation du risque sismique à l’échelle locale. Cette thèse s’intéresse particulièrement à la quantification des effets de la présence du bâti sur l’aléa sismique local dans une vallée sédimentaire et à la caractérisation de paramètres dynamiques sensibles à l’interaction sol-structure à partir de données expérimentales de vibrations ambiantes et de modèles numériques 3D. Elaboré dans le cadre du projet Ritmica soutenu par l’IDEX JEDI de l’Université Côte d’Azur, l’objectif de ce travail de thèse, financée par le Cerema, est d’évaluer l’impact respectif de la stratigraphie du site, de la géologie et du bâti sur l’aléa sismique. Pour cela, une des zones les plus sismiques et à enjeux forts en France métropolitaine est choisie pour cas d’étude : la basse vallée du Var. De nombreuses expérimentations y ont été réalisées depuis plusieurs années, incluant des instrumentations de bâtiments, d’ouvrages d’art et de sol qui ont permis de définir et décrire la configuration géologique de la vallée et le comportement dynamique de certaines des structures environnantes.Dans l’objectif de mieux caractériser l’aléa sismique dans la vallée du Var en prenant en compte la présence des constructions existantes, plusieurs campagnes de mesures de vibrations ambiantes ont été réalisées sur le bassin et sur le rocher de la vallée et également, au niveau et au sein des plus hauts bâtiments de la zone. Ces données permettent d’une part, de définir le modèle géotechnique 3D de la vallée à partir des données géotechniques et géophysiques disponibles et d’autre part, de calibrer un modèle numérique simplifié de bâtiment dans le but d’établir un modèle 3D en élément finis de la vallée intégrant le bâti en surface. Ce modèle sert ensuite à simuler numériquement la propagation des ondes sismiques dans la vallée du Var en utilisant un séisme simulé. Le modèle de sous-sol de la vallée permet de mieux délimiter l’interface bassin-substratum et les vitesses d’ondes sismiques qui constituent des éléments importants dans l’étude des effets de site. Ce modèle montre que l’épaisseur du bassin augmente du Nord vers le Sud allant de 50 m d’épaisseur à plus de 100 m sous l’aéroport de Nice avec des vitesses Vs moyennes aux alentours de 400 m.s-1. Une étude numérique réalisée à partir de cinq modèles de bâtiment en éléments finis (4 de faible hauteur et un de grande hauteur, en béton armé et maçonnerie) montre que les effets de l’ISS sont plus importants pour les bâtiments de type cantilever et que les irrégularités horizontales de rigidité jouent un rôle majeur dans l’ISS. Les campagnes d’instrumentation de bâtiments dans la vallée du Var ont permis d’obtenir un large jeu de données pour l’identification des comportements dynamiques des bâtiments, l’étude de l’ISS et la caractérisation de la variabilité spatiale du mouvement du sol. Ces campagnes denses permettent de vérifier que le premier mode de déformée des bâtiments, par la suite utilisé dans la calibration de modèle simplifiés à partir d’une relation simple, correspond à un mode de flexion. L’analyse du spectre de basculement et des fonctions du décrément aléatoire est utile pour la caractérisation de l’ISS à partir des séries temporelles verticales à la base des structures. Afin d’étudier l’influence combinée des effets de site et du bâti sur le champ d’ondes sismiques en surface, la propagation des ondes sismiques a été numériquement simulée dans cinq modèles 3D en éléments finis différents calibrés à partir d’enregistrements de vibration ambiante et incluant ou non plusieurs types de configurations de villes.