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The installation of vibration-based structural health-monitoring systems relying in the study of natural frequencies to assess the condition of civil engineering structures is becoming more and more common. The extraction of these monitoring features can be achieved through automated operational modal analysis, combining output-only identification methods with cluster analyses, and comparing the identified modal properties with references, in a process known as modal tracking. However, changing environmental and operational conditions affect the dynamic behaviour of structures, disturbing the process of modal tracking, which may lead to the loss of important information and to misidentifications. In this context, this paperproposes a new methodology for modal tracking within the scope of automated operational modal analysis, especially prepared for scenarios with strong external influence on modal properties. A concrete arch dam with large variations of some natural frequencies is used as case study, and the proposed methodology is compared to a standard procedure using a quite unique monitoring data set continuously collected for 3 years.

Neste artigo apresenta-se a formulação e resultados da aplicação de dois modelos descontínuos tridimensionais que simulam a interação hidromecânica. Nestes modelos o comportamento mecânico é simulado de forma idêntica mas o comportamento hidráulico é simulado com duas abordagens diferentes. O primeiro modelo baseia-se numa formulação que admite o escoamento através de elementos planos de interface. O segundo modelo, que se propõe neste artigo, baseia-se numa discretização unidimensional, ocorrendo o escoamento através de elementos de canais. Os modelos hidromecânicos implementados no módulo computacional Parmac3D Fflow são verificados e validados através de exemplos simples, e o modelo proposto é calibrado de modo a serem obtidos, com os dois modelos, os mesmos valores de pressão e de caudal. Foi desenvolvido um modelo hidromecânico de um conjunto barragem/fundação, tendo em consideração a existência de cortina de impermeabilização e de sistema de drenagem na fundação. Salientam-se as vantagens do modelo proposto no estudo do comportamento hidromecânico de fundações de barragens.

Earthquake damage in historic masonry buildings is generally caused by the collapse of individual portions thatbecome detached form the structure and fail by overturning. These mechanisms are mainly governed by thediscrete nature and geometry of the block units. Analyses based on explicit micro-modelling in which each blockis considered separately are therefore of increasing importance. This paper offers a robust tool for the seismicassessment of masonry structures under either, quasi-static or dynamic loading. Algorithms for performing dynamicpulses and pushover analyses through the Discrete Element Method are developed and described, takinginto account the actual discrete nature and geometry of masonry. A numerical procedure is proposed thatautomatically detects the collapse mode and follows the evolution of the analysis until collapse. The implementedmethod is able to give a reliable estimate of the expected failure mechanism, providing the seismicacceleration required to trigger the motion and the ultimate displacement beyond which the collapse occurs.Finally, the implemented algorithms are applied to two case studies and the results are compared with thetraditional analysis based on rigid-block kinematics to outline the features and potentialities of the proposedapproach.

Conservation of the European-built heritage is nowadays closely related to interventions in masonry construction. Since a significant part of these structures are located in earthquake prone zones, designing protective measures that ensure their preservation requires the assessment of the associated seismic vulnerability and the understanding of their degradation mechanisms. However, due to the presence of discontinuities between its constituent elements, the numerical simulation of the non-linear response of masonry structures subjected to strong earthquakes is a cumbersome task, especially when performed using the traditional finite element method. As an alternative, the discrete element method is particularly suitable for the numerical analysis of such structures under large, damaging loads. By allowing discrete displacements/rotations of individual bodies, and by automatically recognising new contacts between bodies, while eliminating obsolete ones, this numerical approach can simulate the complete detachment of discrete bodies initially in contact.The present paper illustrates the use of the discrete element method to assess the seismic vulnerability of stone arches. A probabilistic approach allows to consider the variability of theseismic action and the uncertainties in the definition of the material properties. First, an unreinforced masonry arch is considered. Based on non-linear multi-directional incremental dynamic analyses, five damage states are proposed and the respective fragility curves are elaborated. Toimprove the arch

A seismic assessment study of two historical masonry arch bridges, with different geometries and spans, ispresented. The seismicity of the two locations was analyzed in order to define the seismic action to be applied.Artificial ground motion records were generated accordingly, and real ground motions were also used. The twonumerical models were created with a 3D discrete element code. The accuracy of the deformability of the blockmodels was verified by comparison with a finite element model. In situ measurements of the natural frequencieswere available for one of the bridges, providing further means for model calibration. Time domain dynamicanalyses were performed with each set of ground motions, allowing an evaluation of damage and failure modesunder seismic action. The shorter span bridge was found to withstand the regulatory records with minimumdamage. In contrast, the longer span bridge displayed a significant vulnerability to earthquake action. The studyshows that rigid block models have the ability to represent effectively the dynamic elastic response of the bridgesand can be calibrated by ambient vibration measurements. Furthermore, the discrete element models provide apowerful tool to investigate the nonlinear dynamic response and failure of these structures, which has to be basedon a comprehensive set of dynamic records.

Stability analyses of geotechnical structures in rock are traditionally performed using deterministic methods. In Europe, Eurocode7, introduced in the beginning of the 21st century, adopts limit state design and semi-probabilistic methods, using partial factors for the design of geotechnical structures. Meanwhile, reliability-based design, using probabilistic methods, is becoming more common in practical cases. The paper considers an intentionally simple case study?the analysis of a slope in a rock mass with one discontinuity, considered in a discrete way, forming a rock block to be stabilised by anchors?to compare the results obtained with the different methods. The objective is to calculate the force applied by the anchors so that the ultimate limit states of sliding of the rock block is verified. Deterministic-based design optimization considering both the traditional global safety factor approach and the partial factor approach following the Eurocode 7 are first applied. A reliability-based design optimization procedure?which takes geometrical and mechanical properties of the discontinuities as random variables?is then used, and the results are compared to the former ones. A discussion is presented concerning the consistency of the obtained results.

Civil engineering structures are generally supposed to have long operation life spans during which they aresubmitted to many factors, both environmentally and human-induced, that degrade their condition and performance,gradually leading to the occurrence of damages and malfunctions. Therefore, systems capable ofmonitoring and assessing structural performance automatically are highly desirable.In this context, this paper describes the vibration-based structural health monitoring of Baixo Sabor arch dam,in Portugal, detailing results from the several processing stages needed to achieve the ability to detect damage.Automated operational modal analysis is applied to the data obtained during the first three years of monitoring,after which environmental and operational conditions affecting modal properties are studied and their effectsminimised through the combined application of weighted regression models and principal components analysis.Finally, damages are simulated in a numerical model of the dam, and the results are used to test the ability ofdamage detection tools to find these anomalies.The present paper uses a quite unique set of experimental data to test for the first time the ability of avibration-based SHM system to identify realistic damages in an arch dam.

The paper investigates the effectiveness of two-dimensional Discrete Element Method as a tool forstructural analysis of arches provided with buttresses and backfill and strengthened with externallybonded reinforcement. Masonry vault and buttresses are modelled as an assembly of 2Drigid blocks interacting through non-linear contact joints, the backfill is discretized into deformableelastic-plastic triangular elements, while the reinforcement is modelled by means of trusselements bonded to the substrate through non-linear springs. A parametric analysis on theinfluence of material parameters and the effect of the discretization of the backfill is carriedout, and the outcome of different reinforcement systems, consisting of Steel Reinforced Groutapplied either at the intrados or at the extrados, are analysed. The comparison with experimentalfull-scale tests proved the ability of the numerical approach to capture hinges position, loadbearing capability, as well as the increase in deflection and load capacity provided by thereinforcement.

The uplift pressures change the stress state of the rock mass foundation in a coupled hydromechanical process and may compromise the dam stability. Consequently, dam safety regulations specify the maximum values of the hydraulic conductivity and uplift pressures that can usually only be fulfilled after the execution of seepage and uplift control measures. The design of waterproofing and drainage systems is still based on an equivalent continuum approach, even though rock mass foundations are discontinuous media. The analysis of the piezometric monitoring data of several Portuguese large concrete dam foundations reveals that uplift pressures are site-specific and may even vary considerably across a given site, which can be critical for the safety assessment. From the data gathered in several dams, a probabilistic model that can be seen as an a priori prediction model for uplift pressures is proposed. Considering the difficulty in classifying the geologic foundation conditions beneath each piezometer in existing dams, it is assumed that the data come from a mixture of two beta distributions, representing foundations with regular and unfavorable geologic conditions. This model is a significant improvement over available approaches and will be instrumental for the assessment of existing dams and the design of new dams.

The characterization of the dynamic behavior of an arch dam, and its evolutionthroughout the structure's lifetime, provides important data for the safetycontrol process. Forced vibration tests remain a reliable technique for this purpose.The Baixo Sabor dam is a 123 m high arch dam recently built in Portugal.Forced vibration tests were performed before and after the reservoir filling.Two techniques for forced vibration test are compared, discrete frequencyscanning, the standard methodology, and continuous frequency scanning (sinesweep), a new proposed methodology, which allowed faster results withoutloss of precision. For the interpretation of test results two numerical models ofthe dam-reservoir-foundation system were built, and calibrated with the experimentaldata. A good match of numerical and experimental results wasobtained for the six lowest frequencies and corresponding mode shapes.

A determinação da resposta dinâmica das obras e o acompanhamento da evolução do seucomportamento durante as várias fases da vida é muito importante, estando inserido nas atividadesdo controle de segurança estrutural. A realização de ensaios de vibração forçada em barragens debetão para a determinação do comportamento dinâmico continua a ser uma das técnicas mais fiáveisnesta área. Nesta comunicação descreve-se a metodologia de ensaio, e apresentam-se os resultadosrelativos a um caso de estudo, referente à caraterização do comportamento dinâmico da barragemdo de Foz Tua. Foi desenvolvido um modelo numérico, com representação do sistema barragemalbufeira-fundação, para apoio na preparação do ensaio e interpretação dos resultadosexperimentais.

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Neste trabalho analisa-se a estabilidade de uma grande barragem arco-gravidade e dasua fundação procurando avaliar a importância da utilização de um modelo constitutivocom enfraquecimento para o contacto betão/rocha e para os elementos de junta quesimulam o comportamento não linear do betão. O modelo baseia-se numa formulaçãode fenda discreta. Considera-se que o modelo com enfraquecimento se aproxima docomportamento real, pois conduz a resultados próximos dos obtidosexperimentalmente em ensaios de tração e de corte em provetes betão/rocha e betão.A análise de estabilidade da barragem é efetuada com um modelo descontínuotridimensional, tendo em consideração que os resultados obtidos com um aumento dapressão hidrostática são equivalentes aos obtidos usando o método de redução dasresistências. Verifica-se que para esta obra e para os parâmetros de resistênciautilizados, a adoção de um modelo constitutivo frágil não garante, ao contrário do queseria expetável, a definição de um fator de segurança conservativo.

Continuous dynamic monitoring of large arch dams

Os sistemas de monitorização da condição estrutural baseados em vibrações têm sidoimplementados com sucesso em diversas estruturas de engenharia civil, como pontes, coberturas deestádios e geradores eólicos, fornecendo dados importantes sobre o seu comportamento dinâmico epermitindo o estabelecimento de metodologias de deteção de danos com base na evolução daspropriedades modais. Aliando este conhecimento ao surgimento de sensores de baixo ruído edigitalizadores de alta resolução, surgiu a oportunidade de implementar sistemas de monitorizaçãodinâmica contínua em barragens e assim validar a adequação destes sistemas à monitorização destetipo de estruturas, com o objetivo de detetar danos.A deteção de um comportamento estrutural anormal, que pode indicar a ocorrência de dano, podeser baseada em diagramas de controlo e está associada a alterações nos valores dos parâmetrosmodais que, não sendo explicadas por outros fenómenos físicos, sugerem uma alteração na rigidezda estrutura. Para testar estas ferramentas estatísticas, os parâmetros modais obtidos a partir deséries temporais medidas diretamente na estrutura podem ser alterados com danos simuladosnumericamente.Neste contexto, a capacidade de diagramas de controlo para identificar o surgimento decomportamentos estruturais anormais em barragens é estudada neste trabalho usando dadosobtidos a partir da monitorização dinâmica contínua da barragem do Baixo Sabor, uma barragem debetão de um aproveitamento hidroelétrico que começou a operar no final de 2015. Não sendoexpectável detetar danos numa estrutura tão recente, um conjunto de cenários de danos plausíveisfoi simulado usando um modelo numérico, tendo a influência nas propriedades dinâmicas dabarragem sido usada para contaminar os valores das frequências naturais obtidas da monitorizaçãocontínua.

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In this paper, a critical comparison of two of the most common methods for theanalysis of masonry vaults up to collapse is carried on. Innovative 2D Discrete Element (DE)and Finite Element (FE) models have been adopted aiming at capturing the main features ofmasonry single curvature structures mechanical behavior. Two numerical strategies areadopted: a discrete element model and a continuous homogenized model. The first approachprovides an estimate of the collapse load and failure pattern of masonry based on ad-hocimplemented algorithm. The second approach is formulated in the framework of multi-surfaceplasticity and implemented in a FE code for the path-following non-linear analysis of masonrywall described as continuous anisotropic plate. The two numerical approaches are adopted toreproduce the Experimental Campaign of a full-scale Catalan vault with buttresses and backfill,statically loaded at 1/3 span. The failure modes and the crack patterns obtained by the proposedmodels are compared between them and with that observed in the experimental test as well asthe load-displacement response curves. Both the proposed models efficiently capture thebehavior of the vault and, in particular, the backfill deformation and load-spreading effect,hinges position and formation order.

It is known that the initially proposed circular/spherical rigid particle models are not able to match the ratio of the compressive strength to tensile strength that occurs in rock and the predicted macroscopic friction angle was much lower than the known hard rock experimental values. For this reason, several enhancements have been proposed to address these issues, namely the use of a clumped particle logic, the increase of the number of contacts per particle, the adoption of polygonal/polyhedral grain structures. A flexible 2D DEM based particle model that allows deformable particles to interact in a simplified away is presented. The flexible particle model is tested using biaxial tests and Brazilian tests. The results obtained are compared with those obtained with a rigid particle model with similar contact strength properties and with a flexible particle model, where the flexibility is due to the inner discretization of the grain with smaller particles. The results show that the proposed flexible particle model can predict a behaviour similar to a flexible particle model through inner particle discretization that is more computationally demanding. It is also shown that when compared with a rigid model, the flexible model predicts more reasonable indirect tensile strength to direct tensile strength ratio and requires a smaller value of contact fracture energy to give a good agreement with known experimental data.

A modelação da interação, sob excitações dinâmicas, do corpo da barragem com a albufeira éimportante na análise do comportamento da barragem sob ações sísmicas e na análise einterpretação da resposta dinâmica da estrutura sob excitação ambiente e em ensaios de vibraçãoforçada. Nesta comunicação é analisada a interação barragem-albufeira, considerando que o corpoda barragem apresenta aceleração constante no tempo.São estudadas duas barragens gravidade para dois valores de inclinação do paramento de montante,e uma barragem com geometria tipo abóbada. As distribuições de pressão hidrodinâmicas obtidas noparamento de montante são comparadas com a solução experimental proposta por Zangar, para ocaso das barragens gravidade de paramento inclinado, e com a distribuição teórica proposta porWestergaard, para o caso da barragem tipo abóbada.Os resultados numéricos obtidos permitem concluir que um modelo de fluido em deslocamentospermite obter uma solução estável para as geometrias estudadas, em particular quando se utilizamelementos hexahédricos de oito nós subintegrados. Conclui-se também que, em malhastridimensionais irregulares, em barragens gravidade com inclinação significativa e em barragensabóbada, o valor a adotar para o coeficiente de penalização de modo a minimizar os modos decirculação deve ser avaliado cuidadosamente. Demonstra-se ainda a importância do refinamento damalha da albufeira na vizinhança do paramento.

Measured response of a large arch dam. Comparison with FE results

Masonry is a combination of units such as stones, bricks or blocks usually laid in a cementitious or limemortar. It is probably the oldest material used in construction and has proven to be both simple to buildand durable. Over the years, existing masonry constructions have inevitably suffered damage with time.Earthquakes, soil settlements, material degradation and lack of maintenance are the main reasons forthat. Careful and periodic assessment of such structures is necessary in order to evaluate their structuralcapacity and safety levels. However, performing the structural analysis of masonry construction is notan easy task. A review is presented of the main models based on the discrete element method and the available related numerical techniques that have been proposed for the analysis of masonry. The essential assumptions adopted by these models and numerical implementation issues are discussed. Differences between available models are illustrated by applications to various masonry problems including static and dynamic analysis of masonry arch bridges, walls, vaults, domes and ancient colonnades.This book is composed of 17 chapters authored/co-authored by 25 outstanding researchers from 11countries (Canada, France, Greece, Hungary, Iran,Italy, Mexico, Norway, Portugal, UK, USA), whichwere reviewed by 60 referees.

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This chapter consists of two parts. First a general overview is given: the exact definition of the Discrete Element Method is provided, and the main types of existing models are introduced; then the theoretical fundaments of the most important approaches available today for masonry analysis are given. The second part of the chapter focuses on 3DEC, the most widespread commercial DEM code for masonry analysis. This second part begins with a theoretical overview. Application issues for masonry structures are then considered (block material behaviour, contact representation, structural elements like cables or bars etc.). Among the practical examples arches, barrel vaults, walls, coloumns and complete structures (like houses) are presented, including the issues of quasi-static versus dynamic analysis and of block fracture as well. The readers can find helpful advice on how to simulate their own problems most effectively.

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Discrete element models have become a major tool for masonry analysis, allowing a suitable representation of its discontinuous nature and marked nonlinear behaviour. The chapter reviews the fundamental assumptions of the main DEM formulations available. It focuses more specifically on the widely used UDEC and 3DEC codes, explaining their relation with the other approaches, and the most relevant issues arising in their application to masonry. Applications to the main types of structures are reviewed, considering both static and dynamic analyses. Recent research providing comparisons of the numerical models with experimental and field data is particularly covered. The discussion of the different examples is aimed at clarifying the key capabilities of DEM and demonstrating the most effective ways of using it in a variety of masonry analysis situations.

This chapter is focused on the Portuguese experience on the developmentand exploration of systems for continuously monitoring dam vibrations, usingaccelerometers. The pioneer system for seismic and structural health monitoring(SSHM) installed in Cabril dam (the highest Portuguese arch dam: 132 m high) isdescribed in detail. The design of this system was the result of a long-term LNECresearch program, still ongoing. These monitoring systems should include softwaredeveloped to automatically perform the analysis of collected data, including theautomatic comparison with numerical results from 3DFE models. In view of thegood results obtained with the system in operation in Cabril dam since 2008, similarsystems have been installed in other large dams in Portugal, particularly in recentlybuilt dams. Finally, Baixo Sabor dam is presented as an example of a new Portuguesedam with a complete SSHM system, in operation since 2015. Themain experimentalresults obtained for both dams are shown, namely the evolution of natural frequenciesover time, mode shapes and the measured seismic response to earthquake events.

Para verificação do cumprimento das exigências de segurança das barragens,tanto relativamente à funcionalidade (cenários correntes), como em relação àsegurança ao colapso (cenários de rotura), é essencial utilizar modelos de simulação oude interpretação (no caso de obras existentes) do seu comportamento. Estes modelossão idealizações (simplificações) da realidade, tanto no que diz respeito às acções(modelos das acções), como no que respeita à componente estrutural (modelos estruturais).A solução destes modelos, através de adequados métodos de análise, quantificaparâmetros da resposta das estruturas que permitem avaliar a sua segurança, utilizandocritérios de segurança previamente definidos.A validação destes modelos pode ser feita, no caso de cenários correntes,através da sua comparação com os resultados da observação do comportamento debarragens. No caso de cenários de rotura, não existe muita experiência de comparaçãodestes resultados com situações reais: é pequeno o número de acidentes ocorrido e,mesmo nestes, o volume de informação é reduzido. Desta forma, o recurso a métodosexperimentais, para o estudo de cenários de rotura, tem uma importância acrescida.Assim o principal objectivo deste trabalho é contribuir para melhorar a capacidade deavaliação da segurança de barragens de betão envolvendo cenários de rotura pela fundação.Neste trabalho desenvolveram-se dois ensaios experimentais em modelosfísicos: um primeiro envolvendo uma barragem abóbada, para o estudo de cenários derotura da fundação para acções estáticas; e um segundo de uma barragem gravidadeensaiado em mesa sísmica, com vista a estudar a rotura pela fundação para acçõesdinâmicas.A previsão e interpretação dos ensaios foram efectuadas com modelosmatemáticos adequados, que permitiram a sua validação e posterior utilização no estudode outros cenários.

Neste trabalho apresenta-se o sistema para monitorização em contínuo do comportamento dinâmico da barragem do Cabril que foi instalado em 2008, pelo LNEC e pela EDP, referindo alguns dos principais resultados que têm sido obtidos a partir da análise dos dados recolhidos, quer sob excitação ambiente/operacional, quer sob ações sísmicas. Salienta-se a importância do desenvolvimento do software para tratamento, análise e gestão automática dos dados e apresentam-se os programas que têm vindo a ser desenvolvidos no LNEC, em MATLAB, para apoio a este tipo de sistemas, nomeadamente programas de identificação modal (Modal_ID2.0 e Modal_ID_Auto2.0) e programas de elementos finitos tridimensionais para análise do comportamento dinâmico de sistemas barragem-fundação-albufeira (DamDySSA2.0).

This document presents the research plan for the doctoral thesis of LNEC's Junior Research Fellow Margarida Espada. This work, to be submitted to the Faculty of Engineering of the University of Porto (FEUP), will be developed in the Modelling and Rock Mechanics Unit of the Concrete Dams Department, and it is part of the on-going P2I research project DEMRock6m. This work aims at developing more efficient methodologies to perform safety studies and seismic analysis of rock engineering structures, based on discrete element models and in the integrated use of probabilistic models for the geometric and shear strength parameters and for the water pressures in rock discontinuities. This will allow a more realistic definition of the rock mass in discrete element models and an adequate identification of the potential failure mechanisms.

Neste relatório é apresentado o método de Euler para calcular as órbitas do sistema n-corpos,por exemplo, o dos planetas do sistema Solar, tendo em conta a propagação das forçasgravíticas entre o Sol e os planetas e entre os planetas entre si. Apenas requer como dadosiniciais uma observação anterior das órbitas em termos de posição e velocidade. A correcçãoda interacção entre planetas não é suavizada, o que se justifica pelos seus valores. A correcçãorelativista é importante.

As equações de Navier-Stokes são equações de derivadas parciais. As incógnitas nocaso de incompressibilidade consistem no campo de velocidades. As pressões numa 1ªaproximação resultam de um equilíbrio estático.A principal causa de problemas relacionados com a solução destas equações é devida àparcela das acelerações convectivas que está na origem da turbulência.Pesando estas equações e integrando duas vezes por partes obtém-se uma forma fracadestas equações.Em problemas 3D as variáveis independentes são 3 espaciais e 1 temporal. Admite-seque o campo de velocidades pode ser desenvolvido em série de distribuições de Delta deDirac espaciais e suas derivadas com coeficientes funções do tempo. Com funções deteste polinomiais obtém-se a formulação distribucional proposta das equações deNavier-Stokes.

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O objectivo deste relatório é o estudo da matemática aplicada à solução de problemasfísicos de propagação de ondas esféricas com operador espacial biharmónico,consideradas quânticas.As técnicas matemáticas usadas incluem a transformada de Laplace da função de ondaf e o cálculo de sua inversa tal como sugerida por Pipes e Harvill.O método matemático usado para descrever as ondas esféricas quânticas é compequenas adaptações o método causal não-linear descrito por Croca.

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A análise do comportamento de barragens de betão com base em modelos de elementos finitos tridimensionais exige a definição da discretização a adoptar para o conjunto barragem-fundação, ou barragem-fundação-albufeira. A realização desta tarefa sem o recurso a programas de geração automática é muito dispendiosa pelo que tem vindo a ser desenvolvido no NMMF um módulo computacional para geração automática de malhas de elementos finitos tridimensionais especialmente adaptado para a geração de malhas tridimensionais de barragens abóbada. Inicialmente desenvolvido em FORTRAN, o referido módulo computacional para geração de malhas de elementos finitos tridimensionais tem vindo a ser objecto de diversos melhoramentos, os mais recentes centrados ao nível da interface com o utilizador. Assim, apresenta-se neste relatório o módulo computacional

This document presents a back analysis procedure for identification of the elastic parameters of transversely isotropic rock cores, containing an overcoring triaxial strain probe, from the strains measured during a biaxial test. A three-dimensional finite element model was developed to simulate the biaxial test on the overcored rock specimen and to compute the strains at the location of the strain gauges. Different optimisation algorithms were tested and the most suitable one was selected. The back analysis procedure was tested for identification of the five elastic parameters and the two orientation angles that characterise a transversely isotropic rock core. In spite that, with the developed methodology, convergence was reached and all those parameters could be identified, sensitivity analyses demonstrated that the results obtained were not stable and therefore they were not reliable. By introducing constrains based on common practice and previous experience, a stable and robust methodology was achieved: the three elastic parameters, E1, E2 and ?2, are reliably identified using the value of G2 calculated with Saint-Venant’s expression and a fixed value of ?1, while the orientation parameters are obtained from observation of overcored rock. Analysis of the results shows that application of this methodology represents an enormous step forward when compared with the traditional use of isotropy. Besides, the methodology is general and can also be used with other types of overcoring equipment. The five elastic parameters and the two orientation angles obtained can then be used, together with the overcoring strains, to compute the complete in situ state of stress.

This document presents the work developed by the PhD student Margarida Espada in the scope of the course unit Risk Analysis in Geotechnical Works of the Doctoral Program in Civil Engineering of the Faculty of Engineering of the University of Porto (FEUP). This work presents a reliability analysis, using the response surface method (RSM), for the case study of the left bank excavation slopes of the Baihetan arch dam foundation, which is one of the case studies of Margarida Espada's PhD thesis. The aim was to approximate an implicit limit state function by computing safety factors, using a discrete element model of the Baihetan left bank developed in 3DEC software, where the shear strength parameters of two important rock discontinuities were considered as random variables. The probability of failure was then obtained through an iterative process, using approximation methods. This work presents the 3DEC model developed to analyse the stability conditions in the Baihetan left bank and the results of the reliability analysis.

O problema da solução das equações de Navier Stokes é abordado neste trabalhopropondo-se uma técnica de representação das incógnitas deslocamentos e pressõesvariáveis no espaço e no tempo em série de Delta de Dirac e suas derivadas no tempocujos coeficientes se determinam com base na solução de sistemas de equaçõesdiferenciais definidos no espaço (problema com três variáveis espaciais independentesque pode ser estudado pelo método de Monge).

Neste relatório apresentam-se as equações básicas da elastodinâmica linear, as soluçõesfundamentais e o teorema da representação no domínio de tempo e de frequência.Para movimentos finitos de casca formula-se o teorema dos trabalhos virtuais e a suaimplementação pelo método dos elementos finitos.

Neste relatório apresentam-se os principais aspectos da modelação sísmica de barragensabóbada. Assim propõe-se: modelos numéricos de geração de sismos por uma falha; aforma como o sismo actua na barragem; modelos para estudar a influência da albufeirana vibração do conjunto; métodos para solução das equações do movimento; e novasformulações de elementos finitos para o problema estrutural.

In pressure tunnels and shafts, in addition to the mechanical effect that excavation has on the rock mass and the disturbance that it introduces in the water flow, also the contained water can interact from the mechanical and hydraulic points of view with the rock mass. Seepage in fractured rock masses is dominated by the flow that takes place through the joints, and this is highly d(;pendent on their properties, namely aperture and roughness. Joint aperture, in tum, i::; very sensitive to stress changes. Special attention must therefore be paid to the joints in hydromechanical analyses. In this report are presented some studies that were carried out for the hydromechanical characterization of joints of the Alto Lindoso rock mass and numerical simulations of the hydromechanical behaviour of two selected sections of the high pressure circuit.