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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.

Seepage through the foundation is a relevant condition for the structural assessment of concrete dams. The knowledge of the water flow measured in the drainage system installed to reduce the uplift pressure in a dam's foundation is, therefore, a main issue in the safety control of concrete dams. Monitoring systems include measuring devices to determine the water collected from drains and weirs in order to evaluate the amount of water that flows through the dam. In most large concrete dams, both manual and automated water flow measurements are possible.This paper proposes a statistical quality control method for automatic measuring systems based on simultaneous manual water flow measurements and the knowledge of the corresponding measurement uncertainties. Experimental tests performed in a weir of a Portuguese concrete dam are described and paired water flow estimates and corresponding measurement uncertainties are presented and applied to the proposed method. The results of this study show that the method allows statistical quality control of automated water flow measurement systems applied in concrete dam drainage systems.

Foz Tua project, located close to Tua river

Cement based grouts are commonly used for injections in concrete dams as part ofrehabilitation operations of cracked dam bodies and degraded contraction joints.This document addresses aspects such as assessment of the dam

The explicit formulation of a small displacement model for the coupled hydro-mechanical analysis of concrete dam foundations based on interface finite element technology is presented. The proposed 3D hydromechanical coupled model is based on a 2D coupled model that has been recently proposed. This 3D model, as in the 2D version, requires a thorough pre-processing stage to ensure that the interaction between the various blocks which represent the rock mass foundation and the dam is always face to face. The mechanical part of the model, though limited to small displacements, has the advantage of allowing an accurate representation of the stress distribution along the interfaces, such as rock mass joints. The hydraulic part and the mechanical part of the model are fully compatible. The verification and application examples presented in this paper show that the proposed 3D hydromechanical coupled model allows seepage flow through rock masses to be accurately simulated.

A exploração de grandes barragens envolve, em regra, riscos elevados. Por essa razão exige-se um acompanhamento cuidado destas obras, tendo a observação (monitorização, inspeção e ensaios) um papel fundamental nas atividades de controlo da segurança. Os sistemas de observação das barragens incluem, em regra, dispositivos para monitorização de grandezas relacionadas com as ações e com asrespostas térmica, estrutural e hidráulica do conjunto barragem-fundação. A definição destes sistemas é balizada pela regulamentação portuguesa de segurança de barragens.Nas barragens do Baixo Sabor e do Feiticeiro, dada a sua dimensão e importância, para além dos dispositivos tradicionais com leitura manual, foram instalados sistemas de monitorização automática, tecnologicamente evoluídos, com vista a aumentar a frequência de leitura das grandezas mais significativas com recolha manual, a avaliar as ações dinâmicas e os seus efeitos estruturais nas barragens e a ultrapassar as dificuldades de instalação de redes de observação geodésica por jusante.Referem-se os sistemas de recolha manual e os quatro sistemas específicos de monitorização automática, designadamente o RAD (recolha automática de dados), complementar à recolha manual, envolvendo 232 dispositivos e 407 grandezas, o GNSS (Global Navigation Satellite System), destinado à medição de deslocamentos absolutos através de 8 recetores em regime permanente, o SOS (sistema de observação sísmica), para registo de eventos sísmicos utilizando 6 estações remotas instaladas nas imediações das albufeiras e 8 estações instaladas nas galerias das barragens, e o SMD (sistema de monitorização dinâmica em contínuo), apenas na barragem do Baixo Sabor, para avaliação da evolução das características dinâmicas (frequências próprias e modos de vibração) a partir da excitação ambiente, usando 20 acelerómetros uniaxiais de elevada sensibilidade.

A barragem do Baixo Sabor é uma abóbada de betão de dupla curvatura, com uma altura de 123,00 m e um desenvolvimento do coroamento de 505 m, construída entre 2009 e 2014. Localiza-se no trecho inferior do rio Sabor e cria uma albufeira com 1095 hm3, destinando-se à produção de energia hidroelétrica. O projeto e a construção da barragem estiveram a cargo da EDP, que também tem a responsabilidade da sua exploração. O LNEC tem dado apoio continuado à EDP nos aspetos relacionados com a segurança estrutural.Na comunicação apresentam-se os aspetos relevantes da análise e interpretação do comportamento observado da barragem durante o primeiro enchimento da albufeira, ocorrido entre 2014 e 2016. Sendo o primeiro enchimento uma fase crítica da vida da obra, já que corresponde a um verdadeiro ensaio de carga, o controlo da segurança da obra foi realizado através do acompanhamento contínuo do seu comportamento, com base nos planos de observação e de primeiro enchimento da albufeira, para permitir a deteção e mitigação atempada de qualquer tipo de sintoma de desempenho anómalo. O apoio de modelação estrutural foi determinante para a realização de uma coerente interpretação das relações entre as causas e os efeitos.Adotou-se um modelo tridimensional do conjunto barragem-fundação, analisado pelo método dos elementos finitos, considerando o comportamento viscoelástico dos materiais, a variação das ações da água e as variações térmicas que ocorreram no corpo da barragem. Obteve-se um bom acordo entre os resultados numéricos e os resultados da observação contínua da obra, o que confirmou o bom desempenho da barragem e a adequação da modelação estrutural nesta fase tão importante da vida da obra.

Durante a fase de exploração de uma barragem os efeitos da ação térmica podem ter ordem degrandeza equiparável à das restantes solicitações. Assim, e face às suas características de permanênciae repetição, a ação térmica condiciona fortemente o comportamento das barragens, particularmente noque se refere à durabilidade do betão. No presente trabalho descreve-se a análise térmica realizadapara a barragem do Alto Rabagão, evidenciando os principais aspetos a ter em conta para a simulaçãodesta solicitação. São abordadas algumas questões relativas à simulação das condições térmicasambientais, nomeadamente a variação das ações climáticas de acordo com a hora do dia e o dia do anoe a simulação da radiação solar. São analisados os resultados obtidos com diferentes discretizações,com o objetivo de avaliar a adequabilidade do refinamento da malha de elementos finitos para oestudo do efeito em causa.

The paper presents some relevant results of the structural safety activities performed during the first filling of the reservoir of Baixo Sabor dam. After a brief description of the dam and its construction, the monitoring system, the monitoring plan during the first filling of the reservoir and some important results of tests carried out for the characterization of the material rheological properties are presented. The interpretation of the monitoring results is based on their comparison with results of a numerical model that simulates the structural behaviour of the dam and its foundation.

The current document compiles some of the most relevant information concerning thesymptoms and respective causes of common anomalies observed in concrete dam bodies.These include physical degradation phenomena, like abrasion, cavitation and freeze-thawcycles, and chemical reactions, such as expansive reactions and leaching. Themethodologies available to detect, assess and monitor these are addressed as well, with aspecial focus on cracking.

A fully coupled hydromechanical analysis of the water flow through the rock mass discontinuities of three hypothetical gravity dams of different height was carried out. It was assumed that the dams had similar rock mass foundations, and 2D discontinuous models were developed and analysed with the coupled model for dam foundation analysis Parmac2D-Fflow. This paper presents the results of studies done to analyse the influence that the model geometry and the aperture of foundation discontinuities have on the numerical discharges and hydraulic heads. Analysis was done assuming different behaviour scenarios: i) linear elastic and ii) non-linear behavior at the concrete/rock and rock/rock interfaces. Additionally, results obtained during cycles of filling and emptying the reservoir were used to establish the influence lines of the hydrostatic pressure on recorded discharges. The relevance of using fracture flow models of dam foundation rock masses that take into account the coupled hydromechanical behavior is highlighted.

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