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International audience; Floating offshore wind farms have become a gateway to reach locations that are technically and economically infeasible to exploit using fixed platforms. However, the high capital investments and the uncertainty associated with the reliability, capacity factor, technology evolution, electricity demand, and regulatory frameworks negatively affect the cost of energy of this approach. Alternative strategies, such as designing for flexibility, have been shown to increase the value of engineering systems subject to highly uncertain environments. In this article, an analysis based on life-cycle costs and Monte-Carlo simulation is used to determine if floating wind farms with flexible installed capacity result in lower costs of energy than traditionally designed wind farms. Flexibility is introduced using an adaptable platform strategy and an over-dimensioned platform strategy. The results show that the adaptable platform strategy has the potential to reduce the cost of energy up to 18% by increasing the energy generation and the lifetime of some components of the wind farm. Nonetheless, the benefits of flexibility depend on new legislation that allows for lifetime extensions and proper flexibility management policies that utilize the potential built into the systems.

International audience; Electric power distribution systems that link the bulk power grid (generation and transmission systems) to customers are the leading cause of power outages due to their vulnerability to extreme wind events, especially hurricanes. The strength of the wood poles that typically support the distribution lines also deteriorate over time. The vulnerability of the poles is expected to increase due to the potential impact of climate change on both hurricane hazard and wood decay rate. As such, an effective maintenance planning method is required for the vast number of poles supporting distribution lines. This paper presents a framework to optimize the maintenance of a network of wood utility poles. Corrective replacement due to failure caused by hurricanes and preventive replacement due to excessive decay are considered. The objective is to find the optimal inspection interval for the preventive replacement to minimize the long-term maintenance cost. To solve the optimization problem, the decay of the poles is modeled as a stationary gamma process. The impact of climate change on the rate of pole failure and replacement is also investigated. Two locations are considered as case studies: Miami, Florida, and New York City, New York. The period from 2010 to 2099 is considered for the study. The results of the case study show that the optimal inspection/replacement cycle determined using the developed framework results in lower total maintenance costs compared to current typical utility practice. Based on the inspection and replacement costs used in the study, the results show that adopting a periodic preventive maintenance policy decreases the failure rate of the poles but increases the total maintenance cost. However, only the cost of replacing the poles is considered here. Other considerations, such as indirect costs due to power outages and the impact of pole failure on system reliability, can render the adoption of a preventive replacement policy cost-effective. The results also show that climate change can increase the total maintenance cost. Based on current typical utility maintenance practice, climate change can increase the total maintenance cost by up to 8% in Miami and 6% in NYC, depending on the emission scenario considered.

Chloride-induced corrosion and load induced concrete cracking affect the serviceability and safety of reinforced concrete (RC) structures. Once these phenomena occur simultaneously, the prediction of RC structures&rsquo, lifetimes becomes a major challenge. The objective of this paper is to propose a methodology to evaluate the effect of loading and cracking on the mechanism of chloride ion penetration in concrete. The proposed methodology will be based on Bayesian networks. Bayesian networks are useful to update the lifetime assessment based on experimental data as well as to characterize the uncertainties of the input parameters of a chlorination model including a chloride diffusion acceleration factor. The proposed methodology is illustrated with experimental data coming from tests on RC beams subjected to static and cyclic loading before being in contact with a solution containing chloride ions. The characterized parameters are then used to evaluate the effect of these two loading conditions (static and cyclic) on the corrosion initiation time and the corrosion initiation probability. The results obtained indicate that the proposed methodology is capable of integrating loading and chlorination test data for the determination of the probabilistic parameters of a model in a comprehensive way.

Bio-colonisation affects the ageing of materials and the behaviour of offshore structures. Mooring systems and umbilicals belong to the family of slender bodies which are components sensitive to bio-colonisation because of a change of dynamic behaviour due to shape, roughness and mass modifications. However, this stochastic process in time and space is hard to predict. The purpose is then twofold: first, to provide a stochastic spatial model of the bio-colonisation on a mooring line, second, to show that in some defined environmental conditions, such as low wave height, low wind and current velocities, the monitoring of mooring lines tension can help to assess and reduce uncertainty on this model. Therefore, a comprehensive stochastic modelling based on mussels colonisation was carried out using on-site videotapes, experimental campaigns and expert knowledge. We studied the efficiency of a virtual sensing network using this model and a conditional entropy metric. It is first shown that the spatial model fits well with experimental data, and second that a denser medium accuracy sensor network is to be preferred to a single high accuracy fairlead sensor to reduce the uncertainty on the model parameters. It is then worth updating bio-colonisation on mooring lines during the life-time of a floating wind turbine.

Durability of reinforced concrete (RC) structures is affected by certain environmental conditions and operational actions which can reduce their lifetime significantly. Among these actions, this paper proposes a stochastic model that accounts for the combined effects of chloride-induced corrosion, climate change and cyclic loading. Separately, corrosion leads to cross-section reduction, climate change produces changes in temperature and humidity and fatigue induces nucleation and propagation of cracks in the rebars. When considered together, pitting corrosion nucleates cracks while environmental factors affect the kinematics of chloride ingress and corrosion propagation. The proposed approach is illustrated with the reliability analysis of a bridge girder subjected to cyclic loading under various environmental conditions. The overall results indicate that climate change effect induces lifetime reductions ranging between 1.4 and 2.3% if fatigue load is neglected. Under cyclic loading, total lifetime reduction increases up to 7%.

International audience; Reliability assessment of existing timber structures subjected to deterioration processes is an important task to evaluate their serviceability and safety levels. Towards this aim, data collected after inspection campaigns are often used for updating structural reliability and planning future maintenance/inspection activities. Under natural conditions, timber decay involves a large number of uncertainties related to material properties and environmental exposure. These uncertainties are also affected by temporal and spatial variability of associated deterioration processes. In this context, the main objective of this study is to propose a Dynamic Bayesian Network approach for updating the structural reliability of deteriorating timber structures using inspection data. The proposed approach can account for the uncertainties in the decay process and the effect of spatial variability. It is also useful for reliability updating considering the uncertainties of inspection techniques. The proposed methodology is illustrated with the reliability updating of a timber beam subjected to decay deterioration. Results indicate that this approach is useful for evaluating and updating of structural reliability from spatially distributed inspection data. Reliability updating could also be carried out from partial observations at given areas, which is very useful for large-scale infrastructure.

Problems of uncertainty quantification usually involve large number realiza-tions of a stationary spatial Gaussian random field over a regular grid points. This paper analyzes the convergence of the continuous spectral method for generating a stationary Gaussian random field. The continuous spectral method is the classical approach which discretizes the spectral representation integral to construct an approximation of the field within the Fast Fourier Transform algorithm. The method can be used as an alternative of circulant embedding approach when the discrete covariance matrix is not valid. We demonstrate that the method is computationally attractive when the spectral is a smooth function and decreases rapidly to zero at infinity. In such case, The spectral method is a very versatile approach for generating Gaussian stochastic fields. A simulation results are realized using pseudo-random data based on Monte-Carlo simulations to illustrate the theoretical bound of the method regarding the regularity of the random field and its spectral density.

International audience; Global offshore wind technology shows increasing progress evidenced in the recent reports of wind power capacity, expectations of market expansion and international research projects. Colombia is privileged with several types of natural resources (e.g. wind, sun, water) but there is not a clear legal context to regulate sustainable and safe exploitation of the offshore wind energy considered non-conventional. The development of offshore wind technology in Colombia could attend the energy demand when the hydroelectric system presents low electricity generation during dry hydrological conditions and El Niño-South Oscillations events. This paper analyses international actions that have motivated different countries to establish strategies to reduce CO2, and their advances and challenges in implementing offshore wind technology. The review of the administrative framework of renewable energy in Colombia proved the lack of information for implementing offshore wind

International audience; Corrosion is one of the most significant threats for onshore pipelines that may lead to a Loss of Containment (LOC). A LOC poses significant consequences over the surrounding people and environment because of the hazardousness of the transporting fluids, so different efforts have been raised to predict pipe failures, which are commonly based on reliability assessments with limit state functions. These functions are gathered in serviceability, leakage, and ultimate conditions, out of which the last two approaches contemplate a LOC. This paper reviews recognized limit state functions for corroded pipelines, and it discusses their assumptions and applicability. Specifically, this paper focuses on burst limit pressures considering the relevance in the academic literature and Oil & Gas standards. Therefore, a thorough comparison is presented based on failure criteria, acceptable defect dimensions, failure probability, and error prediction based on experimental and numerical burst tests. The objective is to evaluate the level of conservatism of each simplified model depending on the material toughness and the corrosion rate. This review aims to support a reliability model selection in corroded pipelines for future intervention strategies.

International audience; Chloride ingress and carbonation are the main factors leading to corrosion initiation of reinforced concrete (RC) structures. Lifetime assessment and maintenance optimization of these deteriorating structures has been based for several practical applications on analytical predictive models. The literature review shows that there are numerous analytical models of chloride ingress and carbonation. It was also found that comprehensive lifetime assessment requires that the selected models be able to propagate uncertainties in a correct manner. Thus, this paper proposes a methodology for probabilistic sensitivity analysis of analytical models for chloride ingress and carbonation. Given that di↵erent parameter notations were found for each model, a homogenization of notations and generic forms are first proposed. The sensitivity analysis is based on the following indicators: elasticity coecient, Pearson coecient, bias of the mean and standard deviation of the response of the model. The results highlighted which parameters are influential for each model by considering three concrete types. Overall results indicated a higher e↵ect of the non-linearity of the models on the sensitivity indicators. It was found that the level of influence of each parameter depends also on the concrete type and the duration of the exposure to chlorides or carbon dioxide.

Vulnerability of seismically deficient bridges, coupled with their ageing and deterioration, pose significant threat to safety, integrity and functionality of the highway network that could result in significant risks to public safety, traffic disruption, and socio-economic impacts. Given the limited funds available for bridge retrofit, there is a need for an effective management strategy that will enable engineers to identify and prioritise the high-risk bridges for detailed seismic evaluation and retrofit. A practical risk-based preliminary seismic screening technique is proposed in this paper that enables to develop a ranking or prioritization scheme for seismically-deficient bridges. The complex interactions between seismic hazard, bridge vulnerability and consequences of failure are handled in a hierarchical manner. A Bayesian belief network based modelling technique is used to aggregate through the hierarchy and generate risk indices by accounting for chloride-induced corrosion deterioration mechanisms. The efficacy of the proposed method is illustrated on two existing bridges that are assumed to be located in high seismic zones and designed under different standards concerning their structural safety under seismic loads and durability performance.

International audience; The characterization of damages from output-only vibration measurements is an important issue for Structural Health Monitoring (SHM), in particular for bridges under ambient excitation. In the last years, a multitude of methods has been proposed for vibration-based damage detection, lo-calization and quantification. In this work, a benchmark application for such methods is proposed, namely a 1/200 scale model of the Saint-Nazaire Bridge, which is a cable-stayed bridge spanning the Loire River near the river's mouth. The region of interest, the central metallic structure, measures 720 meters. The aim of the instrumentation is to assess the capability of damage assessment methods to assess a cable failure. The model is instrumented with ten accelerometers and excited by white noise. A damage localization method is applied to test the proposed setup, namely the statistical damage locating vector approach (S-SDDLV). With this method, vibration measurements from the (healthy) reference and damaged states of the structure are confronted to a finite element of the reference state. Damage indicators are provided for the different structural elements that are easy to compute, without updating the model parameters, and taking into account the intrinsic uncertainty of noisy measurements.

International audience; Cracking initiation and propagation are frequently recognized as main causes leading to failure of timber structures. Since the kinematics of both processes is largely influenced by environmental conditions, a comprehensive reliability assessment of notched structures should take into account such environmental factors. The main purpose of this paper is to propose a methodology for reliability assessment and updating of notched timber components based on mechanical (A-integral formulation) and reliability (simulation and Bayesian networks) methods, and experimental data. The A-integral formulation is used to estimate energy release rates in modes I and II by taking into account thermal effects; but its numerical implementation is time-consuming for uncertainty propagation. In order to deal with this problem, Bayesian networks were used for reliability assessment and updating. The experimental data used for updating purposes were obtained from measurements of deflection, temperature and relative humidity on a notched beam (Douglas Fir specie) exposed to outdoor environment and constant loading. The whole proposed methodology was illustrated with the reliability assessment and updating of the studied notched beam. The results indicated that the proposed approach is able to integrate measurements of temperature and deflection for reliability updating.

International audience; Concrete is the predominant construction material for buildings, bridges, wharves, and other infrastructure worldwide. A potentially important factor for asset management is the possible influence of climate change. This may alter the environment to which infrastructure is exposed, and in turn may alter the factors known to affect the corrosion of reinforcing steel, including atmospheric CO2 concentration, temperature, humidity, ocean acidification, airborne pollutants, etc. This chapter poses the problem of adaptation of deteriorating RC structures. It describes a framework for evaluating the cost-effectiveness of adaptation measures that accounts for deterioration models, probabilistic methods and cost-benefit analysis. The methodology is illustrated with an example focusing on cost-effective adaptation of existing RC structures placed in the coastal French cities of Saint-Nazaire and Marseille.

International audience; Nowadays, environment effects, and in particular the reduction of greenhouse effect, are one of the most important issues that are of great concern to the research community. As per the Kyoto protocol and the COP 21 meeting, the use of wood in civil engineering structures reminds one solution for the regulation of these effects by minimizing both CO 2 emission and the use of grey energy. Since the wood mechanical behaviour is quite complex due to its anisotropic constitution, the coalescence of various defects (nodes, orientation of annual rings, …) during its service life, the increasing use of wood as structural material in civil engineering is a major challenge, and needs to increase scientific efforts in understanding the mechanical behaviour of timber structures. In order to bring some responses to these scientific problems, the JCJC 2013 CLIMBOIS research project (Moutou Pitti et al. 2014) is dealing with the effects of climatic and mechanical variations on the durability of notched timber structures. Material cracking is one of the most important factors involved in the collapse of structures. However, if the crack initiation is detected earlier, and the monitoring of the crack propagation within the materials is under control, the structural integrity of buildings can be easily evaluated by sending alerts. Within the framework of this research project, the study carried out herein is devoted to both an identification of failure

International audience; The investigation of tropical behaviour woods in their environment is a real challenge for the prediction of the structural responses of tropical timber structures subjected to thermo-hygro-mechanical loadings. The present study is focused on the experimental characterization and modelling of the spatial variability of the physical-mechanical parameters (density, modulus of elasticity, compression and flexion) of a solid wood beam subjected to outdoor conditions in the south of Gabon into equatorial Region. Figure 1: (a) Beams in sheltered outside climate; (b) specimens, (c) cross-sections, (d) Spatial specimen modelling; (e) Experimental device modelling.

International audience; Non-destructive monitoring of crack growth within material becomes an essential tool to better understand cracking mechanisms of materials, and therefore to reduce failure risks. This paper presents results from laboratory static tests that were conducted to investigate the monitoring of crack tip growth within wood material. Double Cantilever Beam specimens with variable inertia were tested in opening mode configuration. Acoustic emission (AE) technique was used to monitor the acoustic activity within wood material. In a first step, the reliability of the crack tip monitoring is evaluated in terms of Probability of Detection (PoD). Results show that for all specimens the PoD is larger than 70% for a detection threshold of 1 mm. In a second step, a K-means++ algorithm was used to perform a cluster analysis of AE data, and to allow the AE events that were generated by the crack tip growth to be identified. Evolutions of both strain energy and AE energy are compared, and the experimental results show that the first AE events appear when the wood material reaches its limit to store strain energy, so at the vicinity of the end of its linear elastic behaviour.Highlights DCB wood specimens with variable inertia were tested in opening mode configuration. Unsupervised classification of AE events to identify three failure mechanisms. Probability of Detection to evaluate the reliability of the crack tip monitoring. Probability of Detection is larger than 70% for a detection threshold of 1 mm.

International audience

International audience; Most of the approaches for diagnosis or prognosis of deteriorated reinforced concrete(RC) structures are based on two stages: acquiring data (concrete properties, quantitative degradation information), and then predicting the evolution of degradation by using appropriate models. Spatial variability of both properties and degradation processescannot be neglected in the lifecycle assessment and implies that (i) data should be acquired for a representative part of the concrete surface and (ii)models should be capable of dealing with this variability.However, the assessment and modeling of spatial variability is not a straightforward task particularly when uncertainties affect the measurementsorwhen the number of measurements is limited.The present paper aims at studying the capability of analytical carbonation models to deal with the spatial variability of model inputs in terms of spatial correlation of model outputs.Analytical models are considered herein because they provide practical and usual tools in engineering. This paper focuses on the case of a RC wallexposed to atmospheric carbonation where concrete properties and carbonation depths were measured by destructive techniques at several points over a linear portion of a wall within the framework of the French ANR EVADEOS project.Uncertainties due to experimental devices and procedures are estimated and propagated throughout random field models to account for spatial variability of spatial observations. Correspondence indexes are proposed to rank carbonation models with respect to their ability of reflecting the observed correlation profiles of carbonation depth. It was found that for the available database the proposed correspondence index that incorporates uncertainties was useful to assess the capabilities of models to deal with the spatial variability.

International audience; This paper addresses the topic of long-term characterisation and probabilistic modelling of chloride ingress into reinforced concrete (RC) structures. Since the corrosion initiation stage may cover various decades, normal tests which simulate chloride penetration into concrete in laboratory conditions as the same as natural conditions, will require significant experimental times. Hence, long-term lifetime assessment of RC structures under chloride attack remains still a challenge. In practice this problem is solved through the use of accelerated tests which speed up the chloride ingress rate and provide valuable mid-and long-term information on the chloride penetration process. Nevertheless, this information cannot be directly used for parameter statistical characterisation if the equivalent times required in natural conditions to reach the same chloride concentrations in the accelerated tests are unknown. Consequently, this study proposes a novel iterative approach based on Bayesian network updating to estimate chloride ingress model parameters from the data obtained under accelerated laboratory conditions. The Bayesian Network structure and iterative approach are first tested with numerical evidences. Thereafter, the complete proposed methodology is verified with results from real experimental measurements. The results indicate that combining data from normal and accelerated tests significantly reduces the statistical characterisation error of model parameters.

International audience; Flexible piezoelectric device has been realized by depositing lead zirconate titanate (PZT) thin films by Chemical Solution Deposition (CSD) onto very thin aluminium foil (16 µm) and using polyethylene terephthalate (PET) laminated film (150 µm) as encapsulation. A ruthenium dioxide layer has been used in order to enhance the quality of the PZT/Al interface, improving the dielectric, ferroelectric and piezoelectric properties of the PZT film. The obtained piezoelectric generators have been subjected to large bending motions at low frequencies ranging from 0.1 to 8 Hz and the experimental values of the output voltage, output current and harvested power have been compared to theoretical values (derived from the electrokinetic model of the piezoelectric material) with a very good agreement. Due to the increase of the permittivity of the PZT film by the use of RuO2 interlayer, moderate decrease of the harvested power at the optimal load resistance is found (from 185 nW to 143 nW at 4.4 Hz), despite the enhancement of the piezoelectric properties. This type of very flexible film able to withstand small radius of curvature (1 cm) may yield promising avenue in the field of low frequency mechanical energy harvesting.

International audience; Chloride penetration is among the main causes of corrosion initiation in reinforced concrete (RC) structures producing premature degradations. Weather and exposure conditions directly affect chloride ingress mechanisms and therefore the operational service life and safety of RC structures. Consequently, comprehensive chloride ingress models are useful tools to estimate corrosion initiation risks and minimize maintenance costs for RC structures placed under chloride-contaminated environments. This paper first presents a coupled thermo-hydro-chemical model for predicting chloride penetration into concrete that accounts for realistic weather conditions. This complete numerical model takes into account multiple factors affecting chloride ingress such as diffusion, convection, chloride binding, ionic interaction, and concrete aging. Since the complete modelcould be computationally expensive for long-term assessment, this study also proposes model simplifications in order to reduce the computational cost. Long-term chloride assessments of complete and reduced models are compared for three locations in France (Brest, Strasbourg and Nice) characterized by different weather and exposure conditions (tidal zone, de-icing salts and salt spray). The comparative study indicates that the reduced model is computationally efficient and accurate for long-term chloride ingress modeling in comparison to the complete one. Given that long-term assessment requires larger climate databases, this research also studies how climate models may affect chloride ingress assessment. The results indicate that the selection of climate models as well as the considered training periods introduce significant errors for mid-and long-term chloride ingress assessment.

This paper reports a simple, quick and cheap method for transferring Pb(Zr,Ti)O 3 (PZT) thin film onto polymer substrate. To achieve a low-cost transfer process, piezoelectric thin film are deposited onto a sacrificial commercial aluminium substrate to target polymer substrate by a wet etching technique. This novel flexible piezoelectric structure was characterized to evaluate its crystal structure and its morphologic properties. This new process should allow to develop novel applications for low frequency vibrations energy harvesting.

International audience; Reinforced concrete (RC) structures placed in chloride-contaminated environments are subjected to deterioration processes that affect their performance, serviceability and safety. Chloride ingress leads to corrosion initiation and its interaction with service loading could reduce its operational life. Chloride ingress and corrosion propagation are highly influenced by weather conditions in the surrounding environment including climate change. Therefore, both structural design and maintenance should be adapted to these new environmental conditions. This study focuses on the assessment of the costs and benefits of climate adaptation strategies for existing RC structures subjected to chloride ingress and climate change. We studied RC structures built at different periods under different construction standards in France. The cost-effectiveness of adaptation measures was measured in terms of the Benefit-to-Cost Ratio (BCR) and the probability that BCR exceeds unity –i.e., Pr(BCR>1). The results of the paper could provide practical advice to policy makers to improve the management of existing RC structures under a changing climate by discussing the influence of the following factors on the mean BCR and Pr(BCR>1): specific exposure conditions, climate change scenarios, risk reduction due to the implementation of adaptation strategies, type of structural component, years of construction and adaptation, discount rates and damage costs.

International audience; The El Niño-Southern Oscillation (ENSO) is an ocean-atmosphere phenomenon involving sustained sea surface temperature fluctuations in the Pacific Ocean, causing disruptions in the behavior of the ocean and atmosphere. We develop a Markov switching autoregressive model to describe the Southern Oscillation Index (SOI), a variable that explains ENSO, using two autoregressive processes to describe the time evolution of SOI, each of which associated with a specific phase of ENSO. The switching between these two models is governed by a discrete time Markov chain (DTMC), with time-varying transition probabilities. Then, we extend the model using sinusoidal functions to forecast future values of SOI. The results can be used as a decision-making tool in the process of risk mitigation against weather and climate related disasters.

International audience; Characterization of randomness and spatial variability of material properties, loading or deterioration processes of structures, from inspection, is a very challenging task that concentrates the improvement of Non Destructive Testing (NDT) tools on more efficient and higher structural coverage. In case of characterization of random loading or material properties, this challenge is arduous because of the limited number of measures and the quasi-infinite potential positions of local failures. This paper presents a two stages procedure for the stochastic characterization of random fields from NDT measurements. According to the stationarity property, the optimal quantity of NDT measurements and their position can be assessed once a quality requirement is included. The proposed procedure allows: (i) to quantify the properties of the ergodic stationary field, and (ii) to assess the second order parameters of the studied random variables. The paper ends illustrating the methodology with an application that considers the inspection of a concrete beam with a capacitive technique. The results indicate that the proposed methodology is useful to identify the parameters of a random field by reducing the number of NDT measures under given quality requirements.

International audience; Concrete biodeterioration in sewers and structures subjected to environments rich in hydrogen sulfide has been related to the activity of sulfur oxidizing bacteria (SOB). In previous studies, the effect of the activity of SOB on concrete structures has been linked mainly to weight loss. In our work we have investigated, in addition to the weight loss, the variations in porosity and compressive strength. The main objective of this paper is to explore, under controlled conditions, the effect of biodegradation of non-submerged samples, on both the physical properties and the mechanical performance. Towards this aim, cement mortar samples inoculated with pure cultures of Acidithiobacillus thiooxidans, Halothiobacillus neapolitanus, and a consortium containing both strains, were exposed to an H2S-rich environment. Changes in physical properties, including weight and porosity, and compressive strength were measured over 300 days. The results showed that the greatest reduction of weight and compressive strength was observed in samples inoculated with the consortium (7 and 52 %, respectively); while the largest variation in porosity was observed in samples inoculated with A. thiooxidans (27 %). These results were used to obtain relationships between the amount of sulfur available over time with specific physical and mechanical properties; i.e., compressive strength, porosity, weight loss, and physical appearance.

The mechanical and physical properties of timber structures could be affected by a combination of loading, moisture content, temperature, biological activity, etc. This paper focuses on the optimal design of new timber structures subjected to fungal decay. Among the optimization methods available in the literature, this study considers a Time-Dependent Reliability Based-Design Optimization approach. This method aims at ensuring a target reliability level during the operational life by considering deterioration and the uncertainties related inherent to materials properties, models and climate. This approach is applied to design optimization of a timber truss subjected to an aggressive (very humid) French climate. The performance of the optimized solution is compared, in terms of safety, with solutions estimated from Deterministic Design Optimization and the classical Reliability-Based Design Optimization approaches. The overall results indicate that the optimized solution obtained by the Time-Dependent Reliability Based-Design Optimization approach ensures the target reliability level during the whole structural lifetime.

In this work, the acoustic emission is used as a measurement technique to detect and locate the progress of the crack tip in a wooden specimen subjected to thermo-hygro-mechanical stresses. Under these stresses, the material response results in the release of energy in the form of transient elastic waves that are recorded by acoustic emission sensors. The post-processing of these acoustic signals is used to detect the position of the crack. There are many parameters that can affect the accuracy of acoustic emission such as noise signals, geometry, wood specie, etc. Consequently, this study combines repetitive tests and probabilistic approaches to characterize uncertainties and improve the acoustic emission protocol. In the experimental program, breaking of graphite mines at various known positions simulated acoustic sources. The differences between the real and detected positions are used to calibrate the tests and to improve the configuration of the sensors., Academic Journal of Civil Engineering, Vol 33 No 2 (2015): Special Issue - ICBBM 2015

The durability of timber structures can be affected by the isolated or combined actions of loading, moisture content, temperature, biological activity, etc. This work focuses on the optimal design of new timber structures subjected to deterioration. Since the deterioration processes and the structural behavior of timber structures are complex, nowadays the deterioration models are not able to account for all influencing factors. Consequently, this study is based on an empirical model that was derived based in-lab experimental studies for the decay growth of brown rot in pine sapwood under variant climate conditions. Such a model is divided into two processes: (i) activation process and (ii) mass loss process. On the other hand, there are significant uncertainties involved in the problem. The uncertainties inherent to materials properties, models and climate are considered throughout a time-dependent reliability based-design optimization (TD-RBDO) approach. The TD-RBDO aims to ensure a target reliability level during the operational life. This approach is applied to design optimization of a new timber component subjected to different French climates. The performance of the optimized solution is compared with a traditional cross-section designed according to the Eurocode 5 in terms of safety. The overall results indicate that an optimized solution ensures a target reliability level during the whole structural lifetime., Academic Journal of Civil Engineering, Vol 33 No 2 (2015): Special Issue - ICBBM 2015

International audience

Many agencies worldwide have to manage structurally damaged reinforced concrete (RC) coastal infrastructure subjected to chloride ingress that require significant repairs. These repairs should ensure optimal levels of serviceability and safety and minimise costs and environmental impact. However, there is a wide range of protocols, techniques and materials for repair and there is not much information about their durability performance. This paper proposes a methodology for evaluating, comparing and/or improving the sustainability of maintenance strategies. It was developed within the framework of the Mareo project in collaboration with the different stakeholders involved during the whole structural lifetime. It is based on probabilistic modelling of deterioration and repair, and the sustainability assessment considers costs (with conventional and intergenerational discounting), carbon dioxide emissions and waste generation. The methodology is illustrated with a numerical example aiming to evaluate and improve the sustainability of a repair technique for RC structures subjected to chloride-induced corrosion damage. Overall results indicate that sustainable solutions increase global costs but they could significantly reduce environmental impact.

International audience; Reinforced concrete (RC) structures are subject to environmental actions affecting their performance, serviceability and safety. Among these actions, chloride ingress leads to corrosion initiation and its interaction with service loading could reduce its operational life. Experimental evidence indicates that chloride ingress is highly influenced by weather conditions in the surrounding environment and therefore by climate change. Consequently, both structural design and maintenance should be adapted to these new environmental conditions. This work focuses on the assessment of the costs and benefits of two climate adaptation strategies for new RC structures placed in chloride-contaminated environments under various climate change scenarios. Their cost-effectiveness is measured in terms of the Benefit-to-Cost Ratio (BCR) and the probability that BCR exceeds unity –i.e., Pr(BCR>1). It was found that increasing concrete strength grade is more cost-effective than increasing design cover. The results also indicate that the cost-effectiveness of a given adaptation strategy depends mainly on the type of structural component, exposure conditions and climate change scenarios.

International audience; Chloride ingress into concrete is one of the main causes leading to the degradation of reinforced concrete (RC) structures. Important damages due to chloride-attack are reported after 10-20 years and thus, structures should be inspected periodically to ensure optimal levels of serviceability and safety. Modelling chloride ingress into concrete, therefore, becomes an important task to plan and quantify maintenance operations of structures. Relevant material and environmental parameters required for modelling could be determined from inspection data obtained after each inspection campaign. However, its assessment requires significant experimental time for collecting data that allow considering the time-dependency of the deterioration process. Data from accelerated test could be used as information about long-term performance of concrete or mortar under real exposure conditions if the scale factor reflecting the ratio between exposures times for natural and accelerated tests is determined. The main objective of this paper is to develop a method based on Bayesian updating to identify the 'real' (equivalent) exposure time from accelerated tests that is used to define the scale factor. The proposed methodology is first tested on simulated data and after implemented to real measurements.

International audience; Highly flexible lead zirconate titanate, Pb(Zr,Ti)O3 (PZT), thin films have been realized by modified sol-gel process. The transverse piezoelectric coefficient d31 was determined from the tip displacement of bending-mode actuators made of PZT cantilever deposited onto bare or RuO2 coated aluminium substrate (16 μm thick). The influence of the thickness of ruthenium dioxide RuO2 and PZT layers was investigated for Pb(Zr0.57Ti0.43)O3. The modification of Zr/Ti ratio from 40/60 to 60/40 was done for 3 μm thick PZT thin films onto aluminium (Al) and Al/RuO2 substrates. A laser vibrometer was used to measure the beam displacement under controlled electric field. The experimental results were fitted in order to find the piezoelectric coefficient. Very large tip deflections of about 1 mm under low voltage (∼8 V) were measured for every cantilevers at the resonance frequency (∼180 Hz). For a given Zr/Ti ratio of 58/42, it was found that the addition of a 40 nm thick RuO2 interfacial layer between the aluminium substrate and the PZT layer induces a remarkable increase of the d31 coefficient by a factor of 2.7, thus corresponding to a maximal d31 value of 33 pC/N. These results make the recently developed PZT/Al thin films very attractive for both low frequency bending mode actuating applications and vibrating energy harvesting.

International audience; Chloride ingress is one of the major causes of reinforced concrete degradation. Chlorides accelerate the breaking of the protective layer of rebars favoring pitting corrosion; furthermore, corrosion products generate cracks in concrete, which further accelerate chloride ingress, increase porosity and reduce the strength. From a chemical perspective, the presence of chlorides and its diffusion into the reinforced concrete matrix is highly influenced by the content and distribution of aluminates (C 3 A), in the same way, in concretes where ultra-rapid strength development and controlled expansion are required the presence of CA determine the chloride diffusion. This can be explained because chlorides react with aluminates to form Friedel's salts and other compounds. Although these reactions have been widely studied, their electrical changes still require further evaluation and analysis. These experimental works use dielectric spectroscopy (DS), a technique that applying an alternating voltage and measuring phase and magnitude of current can determine the dielectric behavior variation. Also, this technique has shown good potential for measuring chlorides in other materials. Within this context, the main objective of this paper is to present the results of a study of the dielectrical behavior of calcium aluminate (in presence of mayenite and other ferrite compountds) when it interacts with solutions of chloride ions (Cl-) at different concentrations (0-1M) using DS. In addition, the paper includes a structural characterization, by SEM, which provides information about changes in the microstructure and the spatial distribution of chemical elements. The results show that changes in dielectric parameters of CA are proportional to chloride content; in addition, chlorides preferentially interact in those zones where Al, Ca, and O are.

International audience; Probabilistic modelling of deterioration processes is an important task to plan and quantify maintenance operations of structures. Relevant material and environmental model parameters could be determined from inspection data; but in practice the number of measures required for uncertainty quantification is conditioned by time-consuming and expensive tests. The main objective of this paper is to propose a method based on Bayesian networks for improving the identification of uncertainties related to material and environmental parameters of deterioration models when there is limited available information. The outputs of the study are inspection configurations (in space and time) that could provide an optimal balance between accuracy and cost. The proposed methodology was applied to the identification of random variables for a chloride ingress model. It was found that there is an optimal discretisation for identifying each model parameter and that the combination of these configurations minimises identification errors. An illustration to the assessment of the probability of corrosion initiation showed that the approach is useful even if inspection data is limited.

International audience; This chapter presents the subset simulation (SS) approach and the Polynomial Cha-os Expansion (PCE) methodology. The SS method is an efficient alternative to the well-known Monte Carlo Simulation (MCS) methodology to calculate small failure probabilities. The basic idea of the SS approach is that the small failure probability can be expressed as a product of larger conditional failure probabilities. On the other hand, the PCE methodology allows one to accurately compute the PDF of a given system response using a reduced number of calls of the deterministic model (as compared to the classical MCS applied on the original complex deterministic model). Indeed, the PCE methodology replaces the computationally-expensive de-terministic model by a meta-model. Once the meta-model is determined, MCS can be applied on the obtained PCE to compute the PDF of the system response with a quasi-negligible computation time.

International audience; In many engineering problems, the uncertainty associated with one random variable needs to be estimated indirectly from the information on uncertainty in another random variable. In most cases, functional relationships (linear or nonlinear) be-tween the response and basic random variables are known; however, in some cases, the exact relationship may not be known explicitly. Since the response variable is a function of other random variables, it will also be random, whether the exact func-tional relationship between them is known or not. The subject of this chapter is the quantification of the uncertainty in the response variable when it is related to other random variables with a known or unknown relationship.

International audience; There are numerous sources of uncertainties that should be considered in engineer-ing design. Reliability analysis methods provide a framework to account for these uncertainties in a rational manner. This chapter presents the First Order Reliability Method (FORM) and the Second Order Reliability Method (SORM). These methods are illustrated by academic examples.

International audience; This work focuses on assessing costs and effectiveness of climate adaptation strategies for existing reinforced concrete structures subject to chloride penetration and climate change. We will study on existing reinforced concrete structures built in France at different years under different building codes. Concerning environmental actions, we considered historical meteorological data and two climate change scenarios. It is hoped that the results of this study provide practical guidance to decision makers to improve the management of reinforced concrete structures under a changing climate.

International audience; Chloride ingress into concrete is one of the major causes leading to the degradation of reinforced concrete structures. Its modelling is an important task to plan and quantify maintenance operations of structures. Relevant material and environmental parameters for modelling could be determined from inspection data that is very limited due to time-consuming and expensive tests. The main objective of this paper is to develop a method based on Bayesian updating for selecting appropriate inspection configuration that can provide an optimal balance between accuracy and cost. The results indicate that Bayesian approach could be a useful tool to identify model parameters even from insufficient inspection data.

International audience; The aim of this work is to handle simplified models of carbonation in a probablistic approach in order to propose an optimized maintenance strategy against steel corrosion. First of all, a synthesis of existing simplified models is presented. Three categories of models have been highlighted. Then a sensitivity analysis is proposed for a ranking of input parameters. Elasticity, linear correlation coefficient of Pearson, impact on the mean and the standard deviation of the models response are the indicators used. Given that corrosion concerns overall a structure surface, a methodology to take into account spatial variability through these models is described in this paper. The method used for describing spatial variability is Karhunen Loeve expansion. When inspections are carried out on the strucure, new data are available. Therefore, an updating process of the spatial variability parameters through bayesian network has been tested in this work. Results show that the updating process works correctly.

International audience; Chloride ingress is one of the major causes of reinforced concrete (RC) deterioration. Free chloride induces the corrosion of rebars, reducing the material strength, and therefore, the structural behav- ior. This paper highlights the importance of chloride content measuring, and also summarizes the state of the art of non-destructive and in situ techniques for measuring chloride content into con- crete structures. These techniques have been developed over the past twenty years, and they have been shown as good alternatives in durability field. They are based on three methods: electrical resistivity (ER), ion selective electrode (ISE) and optical fiber sensors (OFS).

International audience; This paper focuses on assessing the costs and effectiveness of climate adaptation strategies for existing reinforced concrete structures subject to chloride penetration and climate change. We will focus on reinforced concrete structures built in France at different times under different building codes. With regard to environmental actions, historical meteorological data are used to estimate the current state of deterioration and several climate change scenarios will be considered for assessing the effects of climate change. It is hoped that the results of this study provide practical guidance to decision makers to improve the management of reinforced concrete structures under a changing climate.

International audience; Carbonation affects the performance, serviceability and safety of reinforced concrete (RC) structures when they are placed in environments with important CO2 concentrations. Since the kinetics of carbonation depends on parameters that could be affected by climate change (temperature, atmospheric CO2 pressure and relative humidity), this study aims at quantifying the effect of climate change on the durability of RC structures subjected to carbonation risks. This work couples a carbonation finite element model with a comprehensive reliability approach to consider the uncertainties inherent to the deterioration process. The proposed methodology is applied to the probabilistic assessment of carbonation effects for several cities in France under various climate change scenarios. It was found that climate change and local relative humidity have a significant impact on corrosion initiation risks.

International audience; Chloride ingress into concrete is one of the major causes leading to the degradation of reinforced concrete structures. Its modelling is an important task to plan and quantify maintenance operations of structures. Relevant material and environmental parameters for modelling could be determined from inspection data which is very limited due to expensive costs. The main objective of this paper is to develop a method based on Bayesian network updating for improving the identification of model parameters. The results indicate that Bayesian approach could be a useful tool to identify model parameters even from insufficient inspection data.; La pénétration des chlorures dans le béton est l'une des principales causes conduisant à la dégradation des structures en béton armé. Sa modélisation est une tâche importante pour planifier et quantifier les opérations de maintenance des structures. Des paramètres matériau et environnementaux pertinents pour la modélisation pourraient être déterminés à partir de données d'inspection qui sont très limitées en raison des coûts prohibitifs. L'objectif principal de cette étude est de développer une méthode basée sur la mise à jour des réseaux bayésiens pour l'amélioration de l'identification des paramètres des modèles de chloration. Les résultats indiquent que l'approche bayésienne pourrait être un outil utile pour les identifier, même à partir d'un faible nombre de données d'inspection.

National audience; This study aims at quantifying the effect of global warming on the durability of concrete structures exposed to a risk of corrosion induced by carbonation. Various climate evolution scenarios being available, the purpose is to develop a numerical model for carbonation under variable conditions of temperature, relative humidity and CO 2 pressure, suitable for probabilistic approach, so that the scenarios can be compared through the reliability index of a concrete structure exposed to atmospheric carbonation in several cities in France, and following different global warming scenarios. It appears that global warming and global evolution of relative humidity have a significant impact on structural safety.; Cette étude a pour objectif de quantifier l'impact du réchauffement climatique sur la durabilité des structures en béton armé exposées à un risque de corrosion des armatures initiée par la carbonatation du matériau cimentaire. Différents scenarii d'évolution du climat sont envisagés, pour quelques villes françaises, et la comparaison entre eux se fait sur la base de l'indice de fiabilité d'une même structure soumise à ces scenarii. La détermination de l'indice de fiabilité requiert la mise en oeuvre de méthodes probabilistes nécessitant de nombreux appels à un code de simulation numérique, d'où le besoin de développer un outil numérique adapté. A la lumière de cette étude il apparaît que le scenario de réchauffement climatique (évolution du CO 2 , de l'humidité et de la température) a un impact significatif sur la sûreté de l'ouvrage.

International audience; The sparse polynomial chaos expansion (SPCE) methodology is an efficient approach that deals with uncertainties propagation in case of high‐dimensional problems (i.e., when a large number of random variables is involved). This methodology significantly reduces the computational cost with respect to the classical full PCE methodology. Notice however that when dealing with computationally‐expensive deterministic models, the time cost remains important even with the use of the SPCE. In this paper, an efficient combined use of the SPCE methodology and the Global Sensitivity Analysis is proposed to solve such problem. The proposed methodology is firstly validated using a relatively non‐expensive deterministic model that involves the computation of the PDF of the ultimate bearing capacity of a strip footing resting on a weightless spatially varying soil where the soil cohesion and angle of internal friction are modeled by two anisotropic non‐Gaussian cross‐correlated random fields. This methodology is then applied to an expensive model that considers the case of a ponderable soil. A brief parametric study is presented in this case to show the efficiency of the proposed methodology.

International audience; The mini-symposium was organized in collaboration with Kazuyoshi Nishijima (Kyoto University, Japan) and Mark Stewart (The University of Newcastle, Australia). The seven papers presented in this special issue were selected from among 17 technical papers originally submitted to the mini-symposium. Climate projections announce significant future climate changes. Since civil infrastructure has been designed against past climate conditions, climate changecould alsoaffect its serviceability and safety. Therefore, a comprehensive management of climate change risks should consider these new/extreme environmental conditions in order to reduce potential loss of life and assets. This special issuepresentsdifferent types of hazards/actions (floods, sea level rise, extreme wind events, and physical and chemical actions affecting structural durability)for various types of infrastructure (housing, dams, reinforced concrete structures, and energy and water supply networks). Taking into account that climate change consequences depend on design standards and exposure conditions of given locations, this special issue also includes applications to infrastructure located in several countries: Australia, France, Germany, Japan, South Africa and United Kingdom. These applications and studies cover the following topics: - risk assessment of climate change effects on civil infrastructure, - cost-effectiveness and economic viability of climate adaptation technology and engineering measures, - simplified climate models for engineering purposes, and - discussions on the needs for updating engineering standards and processes. It is hoped that this special issuehighlights some of the aspects to be considered on the development of a comprehensive framework of'Climate Adaptation Engineering'to handle climate charge risks in civil engineering. Climate Adaptation Engineering aims atidentifying efficient and cost-effective engineering solutions for climate adaptation. This objectivecan be achieved by integrating climate change science and engineering and itshould provide recommended changes in current engineering practices (design, construction,maintenance, retrofit, etc.) for climate adaptation.