Publications

This study proposes an alternative approach to modeling the failure mechanisms of brickwork assemblages under combined shear

The Western Anatolia Region of Turkey is an important region of high seismic activity.The active dynamics of the region are shaped by a compression and expansion mechanism. This activemechanism is still ongoing and causes strong seismic activity in the region. The Frontinus Gate is amonument in the Roman city of Hierapolis of Phrygia located in southwestern Anatolia. The aim ofthis study is to investigate the seismic behavior of this stone masonry structure using discrete elementmodeling. For this purpose, nonlinear dynamic analyses were performed to simulate the structuralresponse of the gate under seismic excitation. Deformation, damage, and failure patterns induced inthe masonry gate for di erent levels of seismic action are evaluated and discussed. An earthquakewith a return period of 475 years is expected to cause some damage, but no collapse, while for areturn period of 2475 years, the models indicate collapse of the monument.

In this paper three historical masonry minarets in Istanbul, Turkey, are assessed for thedependency between the input harmonic motion and structural response parameters. Theirheights are 40, 73 and 74 m, while the slenderness is 12, 6 and 12, respectively. The discreteelement method is used in dynamic nonlinear analyses. Models were calibrated withmeasured natural frequencies. A series of sine-wave excitations is created for different frequency-amplitude pairs varying between 0.4 and 10 Hz, and between 0.1 and 1 m/s. Fromthe results of dynamic simulations, a general trend was observed for masonry minarets.Especially, slenderness and wall thickness play an important role on their dynamic responseand damage pattern. Dynamic behavior of these minarets cannot reliably be estimated bystatic non-linear analysis. Two engineering demand parameters (EDPs) are defined to characterizethe displacement of the minaret top and the inter-ring shear displacements alongthe minaret body. Damage performance criteria for minarets are proposed based on fourdamage states and tentative limit values are given. We were able to identify the occurrenceof those limit states as a function of frequency and amplitude of sinusoidal input motion.

This study presents a numerical investigation on the fracture mechanism of tension stiffening phenomenon in reinforced concrete members. A novel approach using the discrete element method (DEM) is proposed, where three-dimensional randomly generated distinct polyhedral blocks are used, representing concrete and one-dimensional truss elements are utilized, representing steel reinforcements. Thus, an explicit representation of reinforced concrete members is achieved, and the mechanical behavior of the system is solved by integrating the equations of motion for each block using the central difference algorithm. The inter-block interactions are taken into consideration at each contact point with springs and cohesive frictionalelements. Once the applied modeling strategy is validated, based on previously published experimental findings, a sensitivity analysis is performed for bond stiffness, cohesion strength, and the number of truss elements. Hence, valuable inferences are made regarding discontinuum analysis of reinforced concrete members, including concrete

Nowadays, the management and safety control of large dams is generally based on automatic monitoring, including the socalledseismic and structural health monitoring systems (SSHM), using the latest technology for automatic data measurement,acquisition and transmission. These systems should include software for automatic management and analysis of continuousmonitoring data and software for numerical simulation of the dam dynamic behavior using 3D finite element models. Thissoftware should be designed to provide useful and reliable information to meet the needs and expectations of stakeholders,and to support the studies of researchers and engineers responsible for structural health monitoring. This paper is focusedon the experience gathered from the SSHM system of Cabril dam, a 132 m high-arch dam, in Portugal, that has been undercontinuous dynamic monitoring since 2008. The importance of the software specifically developed for automatic modalidentification, automatic detection of seismic vibrations (distinct from vibrations due to the operation of discharge gates andpower groups), and automatic comparison between experimental data and computed results from a reference finite elementmodel of the dam-reservoir-foundation system, is highlighted. This software includes: (1) the generation of graphics withthe evolution of the identified natural frequencies over time and the comparison with calculated frequencies using differenthypothesis for concrete damage evolution; and (2) a service to automatically send emails summarizing key dynamic monitoringresults to stakeholders to provide the necessary support for informed management and engineering decision making.The main results from SSHM of Cabril dam are presented, namely regarding the evolution of modal parameter over time,considering the influence of water level variations, and the measured response during an earthquake event.

In this study, a novel computational modeling strategy is proposed to estimate the lateral load capacity andbehavior of unreinforced masonry (URM) structures. All commonly noted failure mechanisms are captured viathe proposed modeling strategy using the discrete element method (DEM) in three-dimensions (3D). Masonrywalls are represented as a system of elastic discrete blocks, where the nodal velocities are evaluated by integrating the equations of motion using the central difference method. Then, the mechanical interactions among adjacent blocks are examined utilizing the relative contact displacements and employed in the contact stress calculation. Through this research, a new stress-displacement contact constitutive model is considered and implemented in the commercial software 3DEC, which includes softening stress-displacement behavior for tension, shear, and compression along with the fracture energy concept. The results of the discontinuum models are validated on small- and large-scale experimental studies available in the literature with good agreement. Furthermore, important inferences are made regarding the effect of block size, the number of contact points, and contact stiffness values for robust and accurate simulations of masonry walls.

De acordo com a legislação portuguesa e tendo em consideração o risco sísmico da zona de construção das barragens é obrigatório a implementação de um Sistema de Observação Sísmica (SOS), incorporando instrumentação para caracterizar a ação sísmica induzida nas obras e a respetiva resposta estrutural. Em complemento, têm sido instalados Sistema de Monitoramento Dinâmico Contínuo (SMDC). O SOS permite não apenas a caracterização da ação sísmica, mas também a sua propagação ao longo do maciço rochoso, bem como a resposta estrutural da barragem. O SMDC visa identificar as características dinâmicas da barragem e sua evolução ao longo do tempo, considerando a variação das condições ambientais e operacionais, bem como a possível evolução das propriedades mecânicas dos materiais. Os processamentos são efetuados automaticamente incluindo a caracterização do nível de aceleração e a identificação dos parâmetros modais da barragem. Os valores obtidos pelo processamento automático são armazenados em base de dados, sendo enviados alertas quando são atingidos os patamares de alarme previamente definidos.Os resultados provenientes destes sistemas são comparados com os resultados de modelos numéricos sofisticados, calibrados com o recurso a ensaios experimentais de caraterização dinâmica realizados na obra durante a fase de primeiro enchimento.A combinação da monitorização dinâmica com os modelos numéricos é uma ferramenta fundamental no controlo de segurança estrutural e gestão de risco das barragens.

Today, there are several computational models to predict the mechanical behaviour of masonry structures subjected to external loading. Such models require the input of material parameters to describe the mechanical behaviour and strength of masonry constructions. Although such masonry materialparameters are characterised by stochastic

Nonhomogeneous material characteristics of masonry lead to complex fracture mechanisms,which require substantial analysis regarding the influence of masonry constituents. In this context, thisstudy presents a discontinuum modeling strategy, based on the discrete element method, developed toinvestigate the tensile fracture mechanism of masonry wallettes parallel to the bed joints consideringthe inherent variation in the material properties. The applied numerical approach utilizes polyhedralblocks to represent masonry and integrate the equations of motion explicitly to compute nodalvelocities for each block in the system. The mechanical interaction between the adjacent blocks iscomputed at the active contact points, where the contact stresses are calculated and updated basedon the implemented contact constitutive models. In this research, di erent fracture mechanisms ofmasonry wallettes under tension are explored developing at the unit

During the last decade, many vibration-based structural health monitoring systems have been successfully implementedin different structures such as bridges, towers, stadia and wind turbines, with the aim of studying thestructure dynamics and its evolution over time, eventually detecting the occurrence of novel structural behaviourthat may indicate the presence of damage.Such vibration-based monitoring systems generally rely on the identification of modal properties, which arethen used as monitoring features. Therefore, from operational modal analysis to the tracking of those featuresand finally to data normalization, many processing steps occur that depend on the accuracy of the identifiedmodal properties. Thus, the estimation of the uncertainties associated with the identified modal properties increasesthe robustness of this process.In this context, data obtained from the continuous dynamic monitoring of a concrete arch dam has been usedto evaluate the gains of quantifying the uncertainties of modal properties, evaluating in particular the effect oftaking these uncertainties into consideration when performing automated operational modal analysis, modaltracking and data normalization. Nevertheless, it is observed that the most significant gains of consideringestimates uncertainties occur when these quantities are used for removing outliers during modal tracking.

A segurança de barragens continua a ser uma preocupação actual da comunidade científica,designadamente pelo elevado risco potencial que em regra é inerente a estas obras e pelanecessidade constante do prolongamento da sua vida útil. Para verificação do cumprimentodas exigências de segurança das barragens, tanto relativamente à funcionalidade (cenárioscorrentes), como em relação à segurança ao colapso (cenários de rotura), é essencial utilizarmodelos de simulação ou de interpretação (no caso de obras existentes) do seucomportamento. Estes modelos são idealizações (simplificações) da realidade, tanto no quediz 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,quantifica parâmetros da resposta das estruturas que permitem avaliar a sua segurança,utilizando critérios de segurança previamente definidos. A validação destes modelos pode serfeita, no caso de cenários correntes, através da sua comparação com os resultados daobservação do comportamento de barragens.Com este objectivo, foi implementado pela primeira vez, um sistema de observação sísmica(SOS), numa grande barragem portuguesa. O SOS tem o duplo objectivo da localização deeventos sísmicos e registo da reposta estrutural da barragem a este tipo de solicitação. Para acaracterização da acção sísmica foram implantadas três estações remotas a formarem umtriângulo com cerca de 15km de lado a montante da barragem, adicionalmente foi instaladauma quarta estação a jusante da barragem (fig. 1). O comportamento estrutural é observadoatravés de cinco sismómetros localizados no corpo da barragem (fig. 2). Todos ossismómetros são compostos por acelerómetros tridimensionais, com digitalizadores de 18 bitsligados em rede, e geridos a partir de uma unidade central. As estações remotas comunicamcom a central de comando por transmissão via wireless. Os sismómetros colocados nabarragem estão ligados por cabo de fibra óptica a uma unidade que concentra os dados paradepois os enviar por wireless para a unidade central.Este sistema está em fase experimental de funcionamento, estando a iniciar-se a exploraçãodos registos gerados pelo sistema.Nesta comunicação será descrito o sistema de observação instalado, a sua exploração e análisedos resultados. Os valores observados provenientes deste sistema serão comparados commodelos matemáticos adequados. O modelo matemático da barragem será desenvolvido comelementos finitos representando a abóbada e as juntas de contracção existentes no protótipo,podendo considerar-se o comportamento não linear do material e das juntas.

The most relevant action in the design of underground projects is often the release of the in situ stresses that occurs during the construction stage. Several different field methods are available to measure the in situ state of stress. Some allow the evaluation of the complete state of stress at a given point, while others only supply a single stress component. Interpretation of test results is seldom straightforward. The paper presents a global methodology for the evaluation of the most likely natural stress field given a set of in situ test results. Some case histories are presented as application examples. The first example deals with the case of an underground powerhouse where high horizontal stresses were determined by overcoring tests, which were later confirmed by flat jack tests performed during the construction of access adits. A second one considers the analysis of a testing programme where overcoring and flat jack tests were both performed at different locations during the initial testing programme. The last one refers to the results of overcoring tests in the vicinity of existing underground caverns, which have to be adequately considered in order to estimate the natural state of stress. Global interpretation models are required to transform a set of point wise test results into a comprehensive stress field to be used in design analysis.

Abstract. Portugal is presently facing a new hydroelectricity era, with theimplementation of a large development program including not only the power upgrade ofexisting large hydro schemes, but also the construction of several new ones, almost all ofthem considered in the

Hard soils/ soft rocks (HSSR) are natural materials where the bonds between particles have important contributionto their strength and stiffness. Progressive rupture of these bonds affects irreversibly the hydro-mechanical behaviorof these materials. Most of the existing models follow the idea that bond degradation depends on accumulatedplastic strains. Such is the case of the model used to describe the mechanical behavior observed in oedometer andisotropic compression tests performed on marls.

A análise estrutural de pavimentos para cargas verticais pode ser realizada com base em vários modelos numéricos: método dos elementos finitos, método dos elementos discretos, método da espessura equivalente, e métodos baseados na análise elástica de multi-camada. Neste trabalho édescrita a formulação de um modelo de análise multi-camada com base na equação decompatibilidade de um corpo elástico linear em coordenadas cilíndricas. Vários tipos de solução de pavimentos são analisados, sendo os resultados obtidos com o modelo de multi-camada proposto comparados com os obtidos com um programa de elementos finitos 3D que apresenta uma maior robustez numérica, e com um programa multi-camada equivalente, BISAR.

A aplicação de modelos de identificação modal no domínio da frequência à análise dos resultados de ensaios de vibração ambiental efectuados no corpo da barragem do Cabril mostrou que, para além dos esperados picos espectrais correspondentes aos modos de vibração da barragem também surgem nos espectros da resposta medida outros picos importantes cuja frequência não corresponde a nenhuma das conhecidas frequências naturais da obra. Colocou-se então a hipótese desses picos espectrais estarem relacionados com o comportamento dinâmico da torre das tomadas de água que é uma estrutura auxiliar, porticada, em betão armado, com altura idêntica à da barragem (132 m). Trata-se de uma estrutura que se encontra imersa na albufeira junto ao paramento de montante da obra, e que suporta os órgãos de manobra das comportas das tomadas de água dos dois grupos de produção de energia e da descarga de fundo. Assim, com vista a analisar a referida hipótese de ocorrência de fenómenos de interacção dinâmica entre a torre e a própria barragem, foi desenvolvido neste trabalho um modelo de elementos finitos 3D para analisar o comportamento dinâmico da torre, o qual foi calibrado com base em resultados experimentais obtidos a partir: i) de ensaios de vibração ambiental efectuados no corpo da barragem e na torre, e; ii) de um sistema de observação em contínuo do comportamento dinâmico instalado recentemente no corpo da barragem. Neste artigo apresenta-se também um estudo de previsão do comportamento dinâmico da torre sob acções sísmicas, efectuando a análise no domínio do tempo e pelo método do espectro de resposta.

As barragens são estruturas que representam risco potencial elevado pois em caso de rotura podem causar perdas humanas e materiais importantes. Através da sua observação criteriosa e com recurso a modelos numéricos faz-se a avaliação de cenários de rotura, obtendo-se factores de segurança que servirão como critérios de decisão para acções de reforço e reabilitação.Neste contexto apresenta-se o caso de uma barragem localizada no Canadá cuja análise do cenário de rotura por deslizamento, sugere a aplicação de cabos de ancoragem de modo a serem alcançadas as condições de segurança pretendidas. Previamente é feita uma breve revisão das técnicas de reforço e reabilitação associadas aos principais cenários de deterioração relativos às barragens gravidade de betão e alvenaria.

Small concrete gravity dams are sometimes built using passive steel anchors to enhance their stability for the applied loads. It is important to assess the amount of internal tensile and shear forces resisted by the anchors to verify their structural adequacy. This paper presents the application of the distinct element method to study the magnitude and distribution of internal anchor forces. Comprehensive parametric analyses considering the anchor shear stiffness and the friction angle of the dam-foundation interface have been performed on a small dam 3 m high. The case of several anchors along the section was also investigated. It is shown that (a) the required displacements to induce anchor loads are very small (of the order of 10x10-3 mm of crack opening), (b) that the anchor shear stiffness has small impact in the load share between anchor and concrete, and finally (c) that strength properties of rock-concrete interface play a key role in the structure behavior.

Release of the in situ stresses is often the most relevant action in underground projects. Several different field methods are available to measure the in situ state of stress. Some allow the evaluation of the complete state of stress at a given point, while others only supply a single stress component. The paper presents a global methodology for evaluation of the most likely natural stress field from in situ test results. Some case histories are presented as examples of application. One example deals with the case of an underground powerhouse where high horizontal stresses were determined by overcoring tests, which were later confirmed by flat jack tests performed during the construction of access adits. A second one considers the analysis of a testing programme where overcoring and flat jack tests were both performed during the initial testing programme in different locations. The last one refers to the results of overcoring tests in the vicinity of existing underground caverns, which have to be adequately considered in order to estimate the natural state of stress.

Neste trabalho apresenta-se um processo iterativo de cálculo, com base na análise limite, para determinação do comprimento de fissuras nos planos horizontais de barragens gravidade sujeitos a esforços de tracção e, em consequência, alteração das condições de aplicação da subpressão. Esta ferramenta baseia-se num modelo de dados proveniente de uma aplicação mais vasta que, a partir da geometria da barragem, características do material, nível da água a jusante e montante, condições de drenagem e solicitação sísmica, permite a determinação das condições de estabilidade da estrutura. Faz-se a análise dos dois acidentes ocorridos na barragem de Bouzey, um por deslizamento pela base e o outro por derrubamento parcial da secção, em que a ocorrência de fissuração e o efeito da subpressão tiveram papel determinante.

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 relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto DEMRock6m do P2I/LNEC 2013-2020. Os resultados da atividade desenvolvida são analisados e avaliados em face dos objetivos inicialmente previstos.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto MEBAD do P2I/LNEC 2013-2020, no período 2016-2023. Os resultados da atividade são analisados e avaliados, em face dos objetivos previstos.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto RockGeoStat do P2I/LNEC 2013-2020. Os resultados da atividade desenvolvida são analisados e avaliados em face dos objetivos inicialmente previstos.

The main goal of this report is to present DamDamage3D1.0, a 3D finite element-based program for non-linear static analysis of arch dams, developed using MATLAB. The non-linear simulations are performed using a damage law and an iterative numerical method based on the stress-transfer technique, considering the redistribution of unbalanced forces in each iteration due to material damage. The concrete

The main goal of this report is to present DamDamage3D1.0, a 3D finite element-based program for non-linear static analysis of arch dams, developed using MATLAB. The non-linear simulations are performed using a damage law and an iterative numerical method based on the stress-transfer technique, considering the redistribution of unbalanced forces in each iteration due to material damage. The concrete

In this work we present the version 1.0 of the GDams2D 1.0 program developed for 2D analysis of gravity dams using the finite element method. This initial version of the program is prepared to analyze the structural behavior of gravity dams for static loads, considering linear-elastic behavior, and using Lagrange finite elements of 4 sides, with 9 nodal points. The GDams2D 1.0 program, developed in MATLAB, includes a module for automatic generation of meshes with a great level of refinement (generated from coarse meshes of quadrilaterals, with 4 nodal points at the vertices) and is designed for easy adaptation to non-linear analyzes, using stress-transfer modules such as those recently developed for the DamSlide3D and DamDamage3D programs. After a brief reference to the fundamentals of solid mechanics and to the simplified hypotheses of plane elasticity, the Fundamentals of the Finite Element Method (FEM) are presented, referring in particular the formulation of the four-node, linear and isoparametric, finite element (FE4nos), with two translation d.o.f per node, and the quadrangular FEs of 9 nodes (FE9nos) used in GDams2D 1.0. Based on some examples of application to simple 2D structures whose response is knownanalytically, the advantages of FEs are emphasized in relation to FE4nos and the verification and operability of GDams2D 1.0 is made using various discretizations. Finally, the case of a gravity dam (25 m high) is presented. The dam

The main objective of this work is the development and presentation of a three-dimensional finite element program, DamSlide3D, to study the behavior of gravity dams for scenarios of sliding through the dam-foundation interface. The DamSlide3D, developed using MATLAB, includes cube-type finite elements with 20 nodal points ("serendipity") and finite interface elements with 16 nodal points (joint elements). Initially, we present the fundamental equations of Solid Mechanics, referring to the main simplified hypotheses considered in the computationally implemented formulation, which is presented mathematically as a problem of boundary values using a displacement formulation. For the structure body and for the foundation, the hypothesis of isotropic materials with linear elastic behavior is assumed and for the interfaces the hypothesis of non-linear behavior is considered using the Mohr- Coulomb criterion. The DamSlide3D input data is provided in an excel file and includes structure geometry data, material properties, support conditions and load parameters. As output, the program graphically displays the stress field (principal stresses) and the displacement field (deformed structure). The program was verified throughout three numerical tests with known theoretical solutions. In these tests a simple structure was used, composed by a column discretized in 3DFE. At the contact surface between the column and the base (horizontal surface) it was considered an interface discretized using joint finite elements. A plane surface that crosses the column with a given slope is also considered, discretized using the same type of joint finite elements. In the first test, the field of elastic stresses at the base, due to self-weight (SW) and hydrostatic pressure (HP), was compared with the theoretical results. In the second test the nonlinear column response was studied for different values of thefriction angle at the inclined interface (in this test the structure is only submitted to SW). In the third test, for the main SW + HP loads, the stability of the column is studied for a variation of the friction angle, and for a variation of the water level. In these three numerical tests the results were always consistent with the theoretical solutions. Finally, as an example of application, a gravity dam structural behavior was analyzed considering the non-linear behavior in the dam-foundation interface. The dam was subjected to self-weight and hydrostatic pressure. A parametric study was developed in order to study the dam stability for differentvalues of water level and friction angle.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto CoMatFail até ao final de 2017. É feita a apreciação da atividade desenvolvida, nomeadamente quanto ao grau de cumprimento do plano de trabalhos, bem como dos objetivos específicos e dos indicadores de desempenho propostos na ficha de projeto. São ainda referidas as aplicações dos resultados da investigação em trabalhos contratados ao LNEC e as candidaturas a financiamento externo desenvolvidas no âmbito do projeto. Inclui-se em anexo a ficha do projeto atualizada, que contempla a revisão do plano de trabalhos.

Neste relatório apresenta-se de forma sucinta a descrição da atividade de investigação realizada no âmbito do projeto DEMRock6m no período 2016-2017. Os resultados da atividade são analisados e avaliados em face dos objetivos inicialmente previstos, sendo proposta uma revisão do plano de atividades para os próximos três anos.

Neste relatório apresenta-se, de forma sucinta, a descrição da atividade de investigação realizada no âmbito do projeto RockGeoStat no período 2016-2017. Os resultados da atividade são analisados e avaliados em face dos objetivos inicialmente previstos, sendo proposto um prolongamento do projeto até ao final de 2018.

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.