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The mechanical property characterization of dam concrete is a challenging task mainly due to the use of large aggregate sizes. The properties of dam concrete are often evaluated from wet-screened concrete tests using standard specimen sizes. A physically-based relationship between dam concrete and wet-screened concrete strength properties is currently unavailable.A prediction methodology is proposed which can be used to obtain the compressive and the splitting tensile strength of dam concrete by taking into account the wet-screened strength results, the effect of the specimen dimensions and the effect of the maximum size of aggregate. The predicted results are compared with test results available in the literature and with test results recently obtained during the construction of the Baixo Sabor dam. It is shown that the proposed prediction tool can be used to obtain accurate estimates of dam concrete strength.

The explicit formulation of a small displacementmodel for the coupled hydro-mechanical analysis of concretegravity dam foundations based on joint finite elementsis presented. The proposed coupled model requires athorough pre-processing stage in order to ensure that theinteraction between the various blocks which representboth the rock mass foundation and the dam is always edgeto edge. The mechanical part of the model, though limitedto small displacements, has the advantage of allowing anaccurate representation of the stress distribution along theinterfaces, such as rock mass joints. The hydraulic part andthe mechanical part of the model are fully compatible. Thecoupled model is validated using a real case of a dam inoperation, by comparison of the results with those obtainedwith a large displacement discrete model. It is shown that itis possible to assess the sliding stability of concrete gravitydams using small displacement models under both staticand dynamic conditions.

This paper proposes a methodology for the prediction of the compressive creep strains of dam concrete based on wet-screened experimental results at constant elevated temperature conditions measured in situ. Due to its large aggregate dimensions, the experimental characterization of dam concrete has particular constraints. The wet-screened concrete, obtained by sieving the aggregates larger than a given dimension, after mixing, is used to cast standard specimens and to embed monitoring devices. An experimental in situ installation using creep cells was used to obtain the compressive creep strain development over time for the maturing conditions of the dam core. The study of the effect of wet-screening procedure on creep in compression considers three types of concrete, dam concrete and two wet-screened concretes tested at three loading ages, 28, 90 and 365 days. The comparison between different types of concrete at different maturing conditions requires the definition of a reference state given by the maturity method, using the equivalent age, and relies on the fit of compressive creep strains to the RILEM recommended model B3. To take into account the effect of the aggregate content on the deformability properties of dam concrete, an equivalent two-phase composite model was applied. The equivalent composite model considered the equivalent matrix as the wet-screened concrete and the inclusions as the larger aggregates that are removed during the wet-screening procedure. Predictions obtained with the composite model are close to the dam concrete experimental results, for the tested loading ages.

This paper proposes the use of the maturity method and of a two-phase composite models for the prediction of dam concrete modulus of elasticity.The methodology was validated with test results obtained from experimental in situ setup using creep cells placed in the dam's body, subjected to variable environmental conditions. It is shown that composite models can be used to predict the modulus of elasticity of in situ dam concrete based on the modulus of elasticity of the wet-screened concrete.

The reduced lifetime of geothermal wells is one of the main issues facing the geothermal industry, with cement durability being one of the main causes for shortening of a well's life. While most wells are cemented with American Petroleum Institute (API) class cements, alternative cementing systems are currently being considered. In this paper, the interactions of two alternative cement formulations with a typical geothermal rock formation are compared with a class A cement. This allows understanding of the most critical zone in the geothermal cement, which is the outermost layer where the cement encounters and, consequently, interacts with the exterior harsh environment, including the volcanic formation and brine. The faster setting of white cement and high-alumina cement compared with the well Portland cement seems to reduce the reaction extent with the rock. For all the cements tested, both the increased curing temperature (from 150°C to 290°C) and the use of bentonite as drilling mud significantly decreased the bond between the cement and the rock.

The application of the limit state design (LSD) in the geotechnical area has increased over the last two decades, but this approach is not yet widely used in dam safety evaluation. This study aims to widen the use of the LSD application for large dams, in particular concrete gravity dam foundations. This paper starts with a brief reference to the LSD approach in recently published guidelines for dam design, followed by a detailed description of the LSD formulation when applied to the foundation of concrete dams. The relevance of the joint application of the concepts of ultimate limit states and of numerical methods is highlighted. Comments are made regarding the criteria adopted in order to determine the characteristic values of the material mechanical properties, with an emphasis on discontinuities, taking into account the spatial variability. The sliding safety assessment of the foundation of a concrete gravity dam using the LSD and a discrete element model, both in persistent and in an accidental design situation, is presented. Results led to the conclusion that the LSD methodology may be followed for dam foundation design with the partial factor values prescribed in Eurocode 7.

To improve the effectiveness of concrete dam safety control in real time, a method is presented for theconstruction of decision rules for the early detection of developing failure scenarios. The decision rulesare based on the use of linear discriminant models developed with data obtained through mathematicalmodels of the dam

In its lifetime, a dam can be exposed to significant water level variations and seasonal environmental temperature changes. The structural safety control of a concrete dam is supported by monitoring activities and is based on models.In practice, the interpretation of recorded concrete dam displacements is usually based on HST (hydrostatic, seasonal, time) statistical models. These models are widely used and consider that the thermal effect can be represented by a seasonal function. The main purpose of this paper is to present an HTT (hydrostatic, thermal, time) statistical model to interpret recorded concrete dam displacements. The idea is to replace the seasonal function with the use of recorded temperatures that better represent the thermal effect on dam behavior.Two new methodologies are presented for constructing HTT statistical models, both based on principal component analysis applied to recorded temperatures in the concrete dam body. In the first method, principal component analysis is used to choose the thermometers for the construction of the HTT model. In the second method, the thermal effect is represented by the principal components of temperature of selected thermometers.The advantage of these methods is that the thermal effect is represented by real temperature measured in the concrete dam body. The HTT statistical models proposed are applied to the 110m high Alto Lindoso arch dam, and the results are compared with the HST displacement model.

The purpose of this research work is to identify the effect of the daily variation of the air temperature on the structural response of a concrete dam. It is intended to obtain a better knowledge about structuralbehaviour of concrete dams. In current day to day activities, quantitative interpretation models are used for the assessment of structural dam behaviour of concrete dams. Most models ignore the temperature effect of a wave with a daily variation. However, in dams with automated data acquisition systems this daily effect can be used to anticipate the detection of abnormal behaviour.In this paper, the Short Time Fourier Transform analysis of the residuals is used, obtained by the quantitative interpretation models and measurement data, to identify the signature that the daily variation of the air temperature has on the structural behaviour of a concrete dam. A case study is presented based on the analysis of a horizontal displacement measured on a pendulum, in the Alto Lindoso concrete dam. As a result, the relation between magnitudes of daily variations of the horizontal displacement analysed and the air temperature was defined. The relation obtained can be used to assess if there is alterations or not in the dam response to short period loads corresponding to the daily variations analysed.

This paper presents the application of a methodology which can be used to assess arch dam foundation stability, using the discrete element method (DEM) and the code 3DEC. A global three-dimensional model of a dam foundation was developed, in which some discontinuities were simulated and both the grout and drainage curtains were represented. The model, calibrated taking into account recorded data, was used to carry out non-linear mechanical analysis. The same model was employed to perform a hydraulic analysis, based on equivalent continuum concepts, which allowed the water pressure pattern within the foundation to be obtained. These water pressures were applied on discontinuities involved in the possible sliding mechanism along the dam/foundation interface, and the safety of the dam/foundation system was evaluated using a process of reduction of strength characteristics, with the aim of calculating the minimum safety factors that ensure stability. Results were compared with those obtained with the usual bi-linear uplift pressure distribution at the base of the dam, commonly used in concrete dam design. The relevance of carrying out hydraulic analysis in arch dam foundation failure studies is highlighted.

Os ensaios de betão integral de barragens, produzido com agregados de grandes dimensões, são de difícil execução, requerem equipamentos específicos e têm um custo elevado comparativamente com os ensaios correntes. É recorrente a crivagem do betão integral, i. e., a remoção, após a mistura dos componentes e ainda em fresco, dos agregados de grandes dimensões do betão integral, obtendo-se o betão crivado. Este tipo de betão é moldado em provetes de menores dimensões e é amplamente ensaiado durante a construção.Esta comunicação apresenta uma metodologia para a previsão da resistência à compressão do betão integral a partir de resultados experimentais e de modelos analíticos. A previsão consiste na combinação de duas leis semi-empíricas, a lei de escala e uma adaptação da lei de Abrams. A primeira permite a uniformização da resistência obtida a partir de provetes de diferentes dimensões e a segunda prevê a resistência com base na relação água-materiais cimentícios e na máxima dimensão do agregado.A metodologia foi validada através de um estudo de sensibilidade para determinar o número mínimo de resultados necessário para obter uma boa estimativa da resistência dos diferentes tipos de betões com agregados de grandes dimensões, incluindo o betão integral. O estudo utilizou os resultados de caracterização das propriedades do betão da barragem do Baixo Sabor.

A maioria das roturas de barragens gravidade ocorreu por deslizamento ao longo da superfície de contacto barragem/fundação, de descontinuidades do maciço rochoso, ou de camadas do maciço rochoso de menor resistência. A possibilidade de deslizamento de uma barragem é em regra avaliada com base em técnicas simplificadas de equilíbrio limite, efetuando uma sequência de cálculos em que as características resistentes das superfícies de descontinuidade são progressivamente minoradas. Neste trabalho, a partir de modelos descontínuos bidimensionais da fundação de barragens gravidade, que simulam a interação hidromecânica, analisa-se a estabilidade das obras aplicando modelos constitutivos com enfraquecimento para o contacto betão/rocha, que se entende serem mais próximos do comportamento real desta descontinuidade. Para duas barragens gravidade com alturas diferentes é apresentada inicialmente a análise numérica com base no método da redução de resistências admitindo uma interface betão/rocha com coesão nula. Os resultados são comparados com os obtidos analiticamente com base em equilíbrio de corpo rígido. Demonstra-se a equivalência entre o método de aumento da carga hidrostática e o método de redução de resistência. Posteriormente realiza-se uma análise de estabilidade com base no aumento da carga hidrostática para dois modelos de enfraquecimento para as superfícies de ligação betão/betão e betão/rocha, considerando que a fundação tem um comportamento elástico linear ou um comportamento frágil. Com base neste tipo de modelos é possível identificar modos de rotura do conjunto barragem/fundação mais realistas e obtêm-se, como esperado, fatores de segurança mais elevados.

Os modelos de partículas têm vindo a ser utilizados no estudo do comportamento de materiais quase-frágeis, em particular do betão. Este tipo de modelos permite a consideração da distribuição, quantidade e forma dos agregados no interior de um determinado provete de betão e a obtenção da resposta estrutural para diferentes condições de ensaio (compressão, tração, corte, curta duração, longa duração, entre outros).Esta comunicação apresenta os principais desenvolvimentos dos modelos de partículas, baseados no método dos elementos discretos, para a previsão do comportamento de provetes de betão em ensaios de determinação do módulo de elasticidade e da função de fluência à compressão. Dado que o modelo permite a consideração explícita dos agregados, é possível analisar a interação entre os diferentes componentes e estudar a influência das suas propriedades no desenvolvimento da deformabilidade e da resistência do betão.Os resultados do estudo mostram que, uma vez calibradas as diferentes propriedades dos contactos entre as partículas de argamassa, de agregado e da interface pasta de cimento-agregado, o modelo de partículas permite a simulação da resposta macroscópica do provete de betão para solicitações impostas em ensaios correntes.

To understand the performance of the dam during the first filling, it iscrucial to predict in real time the displacement and the stresses due to the waterreservoir level and environmental conditions. Particular attention must be givento environmental actions which have a significant effect on arch dams. Hence, acorrect simulation of the first filling should entail, amongst other, a proper tran-sient heat transfer analysis to determine the temperature distribution in the dam.The purpose of this paper is to describe the main issues concerning the struc-tural and geotechnical modelling as well as the heat transfer and boundary con-ditions simulation necessary to obtain a representative behavior of the dam duringthe first filling.An example of numerical simulation of the behavior of an arch concrete damduring the first filling of the reservoir is also given. The temperature distributioninside the dam was estimated using a finite element model which considered theeffects associated with air temperature, water temperature and solar radiation.The structural response of the dam was assessed using the same finite elementmodel. In this case, the contraction joints and the contact surface rock/concretewere included in the model and represented by zero thickness interface elements.The validation of the computed temperatures and the induced displacements wasperformed by comparison with the values measured with the monitoring systeminstalled in the dam.

The Foz Tua Project is the latest accomplished hydroelectric investment of EDP - Energias de Portugal, located in a tributary of Douro River, close to its mouth, in the northeast of Portugal, which includes a concrete double curvature arch dam 108 m high with a total crest length of 275 m, closing a narrow granitic valley.After a brief presentation of the project, the monitoring system is introduced, reporting namely the automatically controlled remote observations.The overall characterization of the behaviour evolution is presented, noticing the perceived agreement between observations in redundant systems, as well as the sought correlation between related physical quantities.Furthermore, some minor inelastic behaviours related to local adjustments of the dam/foundation structure, as well as the improvements in the designed foundation drainage and piezometric networks which were implemented accordingly to the foundation hydraulic behaviour observed in the last impoundment stages, are also commented.Bearing in mind the adequate behaviour during the first filling of the reservoir and the good fitness of a nonlinear finite element model it was concluded that the dam is apt to the following serviceability state.

Monitoring is a key activity to ensure the structural safety of dams and is used for detection of deterioration, including local degradation issues and more extensive deterioration scenarios, such as the development of internal expansion reactions which, in the worst case scenario, can lead to severe cracking and even to the abandonment of the dam.This paper presents an overview of an information system that includes a monitoring database, which includes the records of the main actions (water level, air and water temperatures and temperature inside the concrete) and of the main structural responses (radial and tangential displacements measured in inverted plumb-lines and using geodetic techniques, displacements measured in rod extensometers and by precision levellings in target points, joint displacements measured in joint meters, bi- and tridimensional strain fields measured in sets of strainmeters). The hydraulic behaviour of the foundation is also monitored, including the measurement of water discharges along the drainage gallery and the water pressure in the foundation (uplift). The database has monitoring data since the construction period of each dam until this date through periodic readings over the years.Different measurements in some dams, with and without identified deterioration processes, are presented and compared in order to showcase the importance of monitoring activities over the structures lifetime.

This paper presents a methodology for the prediction of dam concrete instantaneous and long-term deformability properties using discrete element method (DEM) based on particle models (PM). The concrete mix, namely the content, size and distribution of the aggregates is explicitly taken into account. This type of concrete has large aggregate size and fraction volume. Due to the computational cost of the analysis of a large number of particles, dam concrete specimen is represented by an arrangement of mortar particles and of coarse aggregates particles. The overall behaviour is determined by the micro properties at each contact type, i.e., mortar-mortar, aggregate-aggregate, and aggregate-mortar which defines the interfacial transition zone (ITZ).The proposed approach is to characterize and model both the mortar and the coarse aggregates separately and study their interaction in the heterogeneous model of concrete. For the mortar, a long-term analysis is required for modelling the aging viscoelastic properties. For the aggregates, an elastic analysis defines the contact micro properties in order to obtain the macro properties of the intact rock.The numerical results obtained from the dam concrete particle model using DEM show a good agreement with the available experimental results for several loading ages.

The Ribeiradio-Ermida multipurpose hydro scheme, built between July 2010 and the end of 2015, is the first major project in the Vouga River basin and is located in the centre of Portugal. Its main purposes are power generation, water supply and flood control. The Ribeiradio dam is a 83 m high concrete gravity dam, with a controlled gated spillway over the dam structure. This project encompasses a second lower dam, Ermida, located 5 km downstream, to regulate Ribeiradio flows. Both schemes are under operation since the first quarter of 2016.This paper presents the main features and results obtained during the first filling of the Ribeiradio dam reservoir and during the subsequent period of exploitation until the end of 2017. In accordance with the Portuguese legislation, the results of the detailed inspections of the dam and its foundation, as well as the integrated analysis of all results provided by the monitoring system, which are presented in the paper, have shown both the dam and its foundation present a satisfactory behaviour.

The failure of dams with large reservoirs can be the cause of catastrophic accidents with very important losses of human lives, material and environmental assets. For these reasons, the safety control of these constructions is regulated and followed by national authorities, considering the structural, hydraulic-operational and environmental aspects. In Portugal, the national authority is technically assisted, for dams that involve major risks, by the National Laboratory for Civil Engineering (LNEC).The structural safety control of dams is based on regular inspection and on the interpretation of data collected from the monitoring system, obtained from different measurement instruments installed according to the dam safety monitoring plan, and taking into account the results of numerical models, considering the material properties and the loads.Baixo Sabor dam, which is owned and was engineered and constructed by EDP-Energias de Portugal, is a good example of the technology and experience in the field of monitoring and instrumentation available in LNEC and in the Faculty of Engineering of the University of Porto (FEUP), able to analyze the behavior of the structure in all phases, namely during the first filling of the reservoir and exploitation period. Some results collected from different measurement instruments are presented, showing the proper functioning of the monitoring system.

To show how quality control of data, statistics, Machine Learning, and Artificial Intelligence will change Infrastructure Safety and Risk Management and Public Safety Forever is expected with the RESTATE project. This work aims to develop methodologies and procedures to support decision-making for the timely safety control of large infrastructures under operating conditions. This project aims to address new methodologies based on Deep Learning to create value in three main activities: quality control of monitoring data, analysis and interpretation of the structural behaviour, and safety assessment.

Nowadays, organizations are embracing digital transformation, investingin the integration of information and communication technology (ICT) toolsand solutions. Advanced ICT technologies converge with operations technologies(OT), allowing machines, processes, employees, and products to be part ofa single data framework, from data collection to analysis, interpretation, and assessment,which are the foundation for informed decision-making. Industry 4.0takes advantage of emergent ICT to make the right decisions, at the right time,optimizing processes, minimizing risks and improving value chains. The mainaim of the structural safety assessment and control of critical infrastructures, suchas dams and bridges, is to protect people, property and the environment fromharmful effects of failure or misoperation of infrastructures. This goal is achievedthrough Structural Health Monitoring and Control (SHMC) activities to monitorand track the life-cycle of critical infrastructures in such a way that it can providesufficient information for long- and short-term decisions regarding structuralsafety assessment. The objective of this work is to present a reflection of the impactof the industry 4.0 trends on the structural safety assessment of critical infrastructuresand, more specifically, to understand the level of maturity and toshow how the leveraging of enabling technologies such as augmented reality,Internet of Things (IoT), additive manufacturing, cloud computing, big data andanalytics are impacting the SHMC activities on critical infrastructures, which aretraditional cyber-physical systems with complex sensor networks used to assessand control structural safety and health.

As atividades de controlo de segurança de barragens de betão têm um caráter preventivo, com o intuito de facilitar a tomada de decisões de forma atempada para evitar ou minimizar as consequências resultantes de um acidente ou incidente de uma barragem. No controlo de segurança de barragens com sistemas de monitorização automática, a análise de uma grande quantidade de dados ainda pode tornar-se uma tarefa difícil. Por um lado, pretende-se garantir o controlo de segurança, em tempo real, mas, por outro lado, a capacidade humana de processar a informação de dados é limitado. No entanto, os desenvolvimentos tecnológicos em termos de capacidade de processamento de informação têm permitido o desenvolvimento de ferramentas para a análise de grandes quantidades de dados. A necessidade de rever os procedimentos de análise de dados adequados para a extração de informação tornou-se um aspeto importante para a tomada de decisão em tempo útil. Por estas razões, é fundamental proporcionar às entidades responsáveis pela segurança das barragens um sistema de apoio à gestão da informação que facilite o acesso aos dados, a interpretação da informação e a tomada de decisão, de forma atempada. Neste contexto, o principal objetivo desta dissertação é a definição de metodologias para: i) melhorar a qualidade das grandezas medidas pelo sistema recolha automática de dados, através da implementação de procedimentos para o controlo da sua qualidade e para a validação dos resultados, tendo em conta a incerteza de medição dos sistemas de medição; ii) melhorar os procedimentos relacionadas com a análise de dados e a sua interpretação, através de uma abordagem baseada nos dados da observação, a fim de apoiar a decisão de quais as grandezas que devem ser incluídas na sistemas de recolha automática de dados, quantificar o efeito da onda térmica diária na resposta da estrutura e reconhecer padrões de comportamento da barragem; iii) a definição de avisos relacionados com a identificação de comportamento anómalo, e de potenciais cenários de rotura. A aplicação das metodologias propostas num sistema de apoio à gestão da informação será um passo sólido para a melhoria dos processos de controlo de segurança em tempo real.

Apresenta-se um estudo sobre o comportamento de fundações de barragens de betão na fase de exploração normal das obras desenvolvido com o objectivo de validar e fundamentar a aplicação de modelos numéricos de análise do comportamento hidromecânico de maciços rochosos, tendo em vista generalizar a sua utilização e tornar mais eficaz a observação e controlo de segurança destas obras. Foi estudada a representação em modelos numéricos da cortina de impermeabilização e do sistema de drenagem e das condições geológico-geotécnicas concretas das zonas de fundação analisadas, tendo em conta, nomeadamente, os problemas computacionais associados a modelos tridimensionais. Foram realizados ensaios de afluência de água em duas grandes barragens portuguesas, uma gravidade e uma abóbada, que se verificou serem fundamentais para caracterizar o escoamento no maciço, complementando a informação obtida com o sistema de observação. Desenvolveram-se modelos hidráulicos e hidromecânicos do comportamento das fundações destas barragens, que no caso da barragem gravidade foram utilizados no estudo de cenários de rotura. Apresentam-se conclusões sobre a adequação e limitação dos modelos numéricos utilizados, sobre os parâmetros essenciais para calibrar e aplicar esses modelos, e propõem-se métodos de planeamento e utilização dos sistemas de observação de fundações de barragens, de modo a melhorar o controlo de segurança.

O presente trabalho pretende contribuir para o aperfeiçoamento dos modelospara análise do comportamento de barragens de betão ao longo do tempo, submetidasa processos expansivos devidos a reacções químicas de origem interna. Odesenvolvimento destas reacções expansivas, determinado pela composição do betãoe influenciado pelos campos térmico, higrométrico e de tensões, pode provocarfissuração e contribuir para a deterioração precoce das obras.O trabalho aborda, na parte inicial, a fenomenologia dos processos expansivos,salientando-se os factores de natureza física e química que mais os influenciam. Deseguida apresentam-se os aspectos relacionados com a identificação e acaracterização das reacções expansivas, no que respeita às evidências físicas e aosseus efeitos estruturais. Analisam-se, entre outras obras, as barragens portuguesasafectadas por esta patologia.A influência dos factores que regulam o desenvolvimento do processoexpansivo (composição do betão, temperatura, humidade e estado de tensão) équantificada com base num modelo de interacção químico-mecânico, permitindo umaestimativa das expansões à escala das obras de engenharia. Este modelo foiintegrado num código computacional de elementos finitos que considera ocomportamento diferido do betão, através de um modelo viscoelástico com maturação,e o surgimento e propagação da fendilhação, por meio de uma formulação de dano.Utiliza-se uma técnica incremental na discretização das acções que permite simular aevolução do comportamento ao longo do tempo, tendo em conta os fenómenosdiferidos e o progressivo desenvolvimento da fissuração.Apresentam-se dois estudos de aplicação a barragens portuguesas afectadaspor processos expansivos. O primeiro estudo refere-se à barragem de Santa Luzia,uma abóbada construída entre 1939 e 1943, em que a magnitude das expansões émoderada. O segundo estudo reporta-se à barragem de Pracana, uma obra decontrafortes cuja albufeira foi mantida vazia durante mais de uma década após trintaanos de exploração, devido à fendilhação generalizada da sua estrutura provocada porgrandes expansões diferenciais, que depois foi reabilitada, encontrando-se desdeentão em exploração normal há cerca de quinze anos. Os resultados destes estudosdemonstram o interesse e as potencialidades das metodologias desenvolvidas naquantificação do processo expansivo, na interpretação do comportamento observado ena avaliação das condições de segurança das obras.

This work deals with the estimation of the parameters of mixtures of beta variables. The work is organized in four main sections preceded by an introduction and succeeded by conclusions. The second section summarizes the properties of the beta distribution and describes two methods to estimate its parameters from observed samples, the method of moments and the maximum likelihood method. The third section presents the general concept of a mixture of random variables, presents the likelihood function of a sample of a beta mixture, finally, describes the EMA