Publications

The Baixo Sabor hydroelectric power plant, located in the northeast of Portugal, includes a reservoir with a storage capacity of 630 million m3 of water created by a concrete double-curvature arch dam, 100 m high, which was equipped with a 20-channel vibration based structural health monitoring system.This paper, apart from describing the dam, presents the main characteristics of the monitoring system and the results obtained during the first 6 months of operation and the first filling of the reservoir. These results include in particular the characterization of the accelerations amplitude and the evolution of the dam modal parameters (natural frequencies, modal damping ratios and mode shapes). It is particular interesting to observe the influence of the water level on the modal parameters and the development of statistical models to mitigate this effect.

Earthquakes cause severe damage to masonry structures due to inertial forces acting in the normaldirection to the plane of the walls. The out-of-plane behavior of masonry walls is complex anddepends on several parameters, such as material and geometric properties of walls, connectionsbetween structural elements, the characteristics of the input motions, among others. Differentanalytical methods and advanced numerical modeling are usually used for evaluating the out-ofplanebehavior of masonry structures. Furthermore, different types of structural analysis can beadopted for this complex behavior, such as limit analysis, pushover, or nonlinear dynamic analysis.Aiming to evaluate the capabilities of different approaches to similar problems, blind predictionswere made using different approaches. For this purpose, two idealized structures were tested on ashaking table and several experts on masonry structures were invited to present blind predictions on theresponse of the structures, aiming at evaluating the available tools for the out-of-plane assessment ofmasonry structures. This article presents the results of the blind test predictions and the comparisonwith the experimental results, namely in terms of formed collapsed mechanisms and control outputs(PGA or maximum displacements), taking into account the selected tools to perform the analysis.

The analysis of the shaking table test of a 3-wall stone masonry structure performed with a discreteelement model is presented. The numerical model, created with the code 3DEC, employed a rigidblock representation and a Mohr-Coulomb joint model. Joint stiffness calibration to match theexperimental natural frequencies is discussed, as well as the boundary conditions to simulate theshake table. Comparisons are made with themeasured displacements at key locations, and themodesof deformation and fracture of the walls. The DEM model was able to reproduce important features ofthe shaking table tests. The experimental deformation and near collapse patterns were clearlyidentifiable in the numerical simulations, which produced displacements within the observed ordersof magnitude, for the various levels of excitation.

This paper 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

The 1:10 scale model of the 15th century Mustafa Pasha Mosque in Skopje, that underwent a comprehensiveshake table program, is modeled by the discrete elements approach. A rigid block model withnonlinear behavior concentrated at the joints was developed and calibrated by comparison with theobserved response. Time domain analyses of the discrete model were performed under the various levelsof dynamic excitation used in the shake table test. Under the lower levels of input, the time and frequencydomain characteristics of the shake table experimental response were fairly well simulated by thenumerical model. This model also predicted well the zones and the level of damages. For the higher inputlevels, the comparison was less satisfactory. Overall, the discrete element approach showed the capabilityto handle the dynamic nonlinear modeling of relatively complex masonry structures.

This work investigates tensile crack propagation in concrete gravity dams by using some recently developed numerical techniques (crack-path field and strain injection techniques). The work carefully addresses aspects related to mesh independence, robustness and computational cost, which are the main issues in fracture modeling. The novel technique consists of a procedure to insert, in the selected domain areas, specific strain fields for enhancing the performance of the underlying finite elements in modeling fracture. Representative numerical simulations of concrete dams show the accuracy and robustness of the methodology.

Block models have been shown to provide a realistic representation of the behavior of many types of masonry structures under static and dynamic loads. When the strength of the units is such that movements along the joints govern the behavior, it is acceptable to make the simplifying assumption that blocks act as rigid bodies. This assumption is particularly useful when dealing with seismic problems, for which the computational times for time domain analysis may be substantial. In this paper, the application of discrete element models for dynamic analysis of masonry structures is addressed. The emphasis is on the seismic behavior of block stone masonry, but the treatment is general to cover other types of masonry. First, the assumptions involved in the choice of a block representation are discussed, stressing in particular the case of rigid block models. Numerical issues are examined, including contact models, calculation of natural frequencies, time stepping algorithms, damping and boundary conditions. A review is presented of modeling examples published in the literature for various types of masonry structures. The choice of numerical representation and its main features are discussed for each case.

Much research in recent years has focused on the seismic analysis of concrete and earthfill dams,and few works have addressed the case of masonry dams. The structural behavior of masonrydams is controlled essentially by its discontinuous nature, which may induce significant nonlinearresponse during an intense earthquake. In this article, a numerical tool based on the Discrete ElementMethod is presented, aimed at the static, dynamic, and hydromechanical analysis of masonry gravitydams. The use of discontinuous models is mandatory for the study of failure mechanisms involvingthe masonry discontinuities, the dam-rock interface or the rock mass joints. The Discrete ElementMethod is able to assemble continuous and discontinuous meshes simultaneously in the same model,providing a versatile tool to consider various assumptions and levels of analysis, ranging from simplifiedto detailed structural representations. A comprehensive study of the seismic behavior of LagoaComprida Dam, located in Portugal, is presented. Both continuous and discontinuous models weredeveloped to assess the main failure mechanisms, including overstress, partial and global sliding,and overturning.

The analysis of the shaking table test of a 3-wall stone masonry structure performed with a discreteelement model is presented. The numerical model, created with the code 3DEC, employed a rigidblock representation and a Mohr-Coulomb joint model. Joint stiffness calibration to match theexperimental natural frequencies is discussed, as well as the boundary conditions to simulate theshake table. Comparisons are made with themeasured displacements at key locations, and themodesof deformation and fracture of the walls. The DEM model was able to reproduce important features ofthe shaking table tests. The experimental deformation and near collapse patterns were clearlyidentifiable in the numerical simulations, which produced displacements within the observed ordersof magnitude, for the various levels of excitation.

A computationally affordable modeling of dynamic fracture phenomena is performed in this study by using strain injectiontechniques and Finite Elements with Embedded strong discontinuities (E-FEM). In the present research, classical strain localizationand strong discontinuity approaches are considered by injecting discontinuous strain and displacement modes in the finite elementformulation without an increase of the total number of degrees of freedom. Following the Continuum Strong DiscontinuityApproach (CSDA), stress

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

Nesta comunicação apresenta-se a modelação de paredes de alvenaria de pedra tradicionalrecorrendo a um modelo de partículas (MP) 2D, baseado no método dos elementos discretos, quetem sido adotado na modelação da fratura em materiais quase-frágeis. Nesta abordagem numérica,os elementos constituintes da estrutura de alvenaria, pedras e a argamassa, são entendidos comosendo formados por um esqueleto de agregados de várias dimensões em contacto direto, comligações do tipo coesivo, que permitem ao esqueleto de agregados suportar forças de tração. Odesenvolvimento dos modelos numéricos apresentados teve por base os modelos experimentaisdesenvolvidos e ensaiados pelo segundo autor [1].Após uma descrição sucinta do modelo numérico, apresenta-se os ensaios experimentais adotadoscomo referência dos estudos numéricos realizados. Descreve-se a metodologia de geração dosmodelos numéricos representativos da estrutura de alvenaria de pedra e apresenta-se o processo decalibração das propriedades dos contactos pedra-pedra e argamassa-argamassa, de modo a se obteruma resposta elástica e resistente próxima da pedra e da argamassa, alcançada nos ensaiosexperimentais.Em seguida são simulados ensaios de compressão simples com base nos parâmetros de contactodefinidos no processo de calibração. Dos ensaios numéricos, verifica-se que, com base nosparâmetros calibrados, os valores de rigidez e de resistência máxima obtida numericamente são daordem de grandeza dos valores obtidos experimentalmente. Os estudos apresentados demonstramque, após calibração dos parâmetros de contacto, os modelos MP permitem representar, com baseem modelos de interação simples, o processo de formação e propagação de fendas em paredes dealvenaria de pedra tradicional, a rigidez, a ductilidade e o valor da carga máxima.

têm sido adotados no estudo da fratura e propriedades viscoelásticas do mastique e dasmisturas betuminosas a partir da representação de uma microestrutura irregular e doscontactos partícula-partícula. Nesse sentido, este trabalho apresenta um modelo departículas tridimensional baseado nos diagramas de Laguerre-Voronoi da estruturagranular para o estudo da viscoelasticidade dos mastiques betuminosos. Dos modelosde contacto existentes, o modelo de Burger é o mais utilizado na análise dos materiaisbetuminosos. Contudo, este modelo apresenta limitações na previsão de propriedadesdinâmicas numa ampla variedade de frequências. Para isso, um modelo de contacto dotipo generalizado de Kelvin (GK) foi desenvolvido para a representação dos contactosviscoelásticos. Este modelo, composto por uma parcela elástica, uma parcelaviscoelástica e uma parcela visco-plástica, é baseado numa formulação incremental, emque o incremento de deslocamento resulta num incremento de força. A conversão daspropriedades macroscópicas, obtidas a partir do ajuste de resultados experimentais emmastiques, em parâmetros de contacto e a respetiva calibração são apresentados. Osmastiques foram submetidos a ensaios cíclicos com carregamento sinusoidal paravalidar o modelo em diferentes temperaturas e frequências. Verificou-se que ocomportamento reológico obtido com o modelo de contacto foi bem previsto. Por fim, osresultados reológicos obtidos com o modelo GK e o modelo de Burger foramcomparados. Como esperado, o modelo de contacto GK apresentou uma melhorresposta quando comparado aos resultados obtidos experimentalmente. Estudos docomportamento dinâmico em misturas betuminosas estão em andamento.

Modelos híbridos de separação de efeitos do tipo HSCT-FE para estudo do comportamento de barragens abóbada

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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.

A brief description of the phenomena and problems associated with underground structures in hydraulic projects is presented, namely in what concerns the powerhouses, surge chambers and pressure tunnels and shafts. An analysis of the calculation methodologies followed in the structural design of this works is presented, as well as of the numerical models usually adopted, namely finite and boundary element models. Finally, some applications of computational mechanics are presented. First, a parameter study for underground powerhouses, with special emphasis in the definition of shapes, existence of several caverns,and in the tridimensional equilibria is described. Afterwards, examples of application to some hydraulic projects are illustrated: a large underground powerhouse in Mozambique, the Alto Lindoso hydroelectric power scheme in construction in the north of Portugal, and the Castelo do Bode tunnel, in operation, integrated in the water supply system to Lisbon.

O presente trabalho aborda a origem do estado de tensão interna dos maciços rochosos e apresenta os factores que o influenciam. Apresentam-se as técnicas e a aparelhagem correntemente utiiizada na determinação do estado de tensão, bem como a interpretação dos ensaios mais comuns, dando-se maior relevo aos ensaios com macacos planos pequenos (S F J) e com o extensómetro tridimensional (S T T),efectuados correntemente pelo LNEC.

Descreve-se sucintamente uma técnica para amostragem linear de descontinuidades em faces expostas de maciços rochosos e referem-se métodos para tratamento dos dados de campo com vista à definição defamílias de descontinuidades e caracterização de uma forma estatística da sua orientação, espaçamento e extensão. Apresentam-se os resultados obtidos para o caso de uma galeria subterrânea no aproveitamentohidroeléctrico do Alto Lindoso. Para as famílias de descontinuidade identificadas apresenta-se um estudo dos blocos tetraédricos que se poderão formar nas diferentes faces de rocha e analisam-se as suas condições de estabilidade.

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Apresentam-se, neste relatório, modelos numéricos baseados no método dos elementos da fronteira, desenvolvidos no LNEC para análise de estruturas subterrâneas. Tecem-se algumas considerações sobre o método dos elementos de fronteira, descrevem-se os modelos desenvolvidos para equilíbrios planos e tridimensionais e apresentam-se alguns exemplos de aplicação.

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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.