Operational modal monitoring of ancient structures using wireless technology

Operational Modal Analysis is currently applied in structural dynamic monitoring studies using conventional wired based sensors and data acquisition platforms. This approach, however, becomes inadequate in cases where the tests are performed in ancient structures with esthetic concerns or in others, where the use of wires greatly impacts the monitoring system cost and creates difficulties in the maintenance and deployment of data acquisition platforms. In these cases, the use of sensor platforms based on wireless and MEMS would clearly benefit these applications. This work presents a first attempt to apply this wireless technology to the structural monitoring of historical masonry constructions in the context of operational modal analysis. Commercial WSN platforms were used to study one laboratory specimen and one of the structural elements of a XV century building in Portugal. Results showed that in comparison to the conventional wired sensors, wireless platforms have poor performance in respect to the acceleration time series recorded and the detection of modal shapes. However, for frequency detection issues, reliable results were obtained, especially when random excitation was used as noise source.

Wind resource modelling in complex terrain using different mesoscale–microscale coupling techniques

Wind resource evaluation in two sites located in Portugal was performed using the mesoscale modelling system Weather Research and Forecasting (WRF) and the wind resource analysis tool commonly used within the wind power industry, the Wind Atlas Analysis and Application Program (WAsP) microscale model. Wind measurement campaigns were conducted in the selected sites, allowing for a comparison between in situ measurements and simulated wind, in terms of flow characteristics and energy yields estimates. Three different methodologies were tested, aiming to provide an overview of the benefits and limitations of these methodologies for wind resource estimation. In the first methodology the mesoscale model acts like “virtual” wind measuring stations, where wind data was computed by WRF for both sites and inserted directly as input in WAsP. In the second approach, the same procedure was followed but here the terrain influences induced by the mesoscale model low resolution terrain data were removed from the simulated wind data. In the third methodology, the simulated wind data is extracted at the top of the planetary boundary layer height for both sites, aiming to assess if the use of geostrophic winds (which, by definition, are not influenced by the local terrain) can bring any improvement in the models performance. The obtained results for the abovementioned methodologies were compared with those resulting from in situ measurements, in terms of mean wind speed, Weibull probability density function parameters and production estimates, considering the installation of one wind turbine in each site. Results showed that the second tested approach is the one that produces values closest to the measured ones, and fairly acceptable deviations were found using this coupling technique in terms of estimated annual production. However, mesoscale output should not be used directly in wind farm sitting projects, mainly due to the mesoscale model terrain data poor resolution. Instead, the use of mesoscale output in microscale models should be seen as a valid alternative to in situ data mainly for preliminary wind resource assessments, although the application of mesoscale and microscale coupling in areas with complex topography should be done with extreme caution.

Development of a meso-microscale coupling procedure for site assessment in complex terrain

A procedure for coupling mesoscale and CFD codes is presented, enabling the inclusion of realistic stratification flow regimes and boundary conditions in CFD simulations of relevance to site and resource assessment studies in complex terrain. Two distinct techniques are derived: (i) in the first one, boundary conditions are extracted from mesoscale results to produce time-varying CFD solutions; (ii) in the second case, a statistical treatment of mesoscale data leads to steady-state flow boundary conditions believed to be more representative than the idealised profiles which are current industry practice. Results are compared with measured data and traditional CFD approaches.

Minimal anomaly-free chiral fermion sets and gauce coupling unification

We look for minimal chiral sets of fermions beyond the standard model that are anomaly free and, simultaneously, vectorlike particles with respect to color SU(3) and electromagnetic U(1). We then study whether the addition of such particles to the standard model particle content allows for the unification of gauge couplings at a high energy scale, above 5.0 x 10(15) GeV so as to be safely consistent with proton decay bounds. The possibility to have unification at the string scale is also considered. Inspired in grand unified theories, we also search for minimal chiral fermion sets that belong to SU(5) multiplets, restricted to representations up to dimension 50. It is shown that, in various cases, it is possible to achieve gauge unification provided that some of the extra fermions decouple at relatively high intermediate scales.

Reappraisal of the wrong-sign HBB¯ coupling and the study of h→Zγ

It has been pointed out recently that current experiments still allow for a two Higgs doublet model where the hbb¯ coupling (kDmb/v) is negative; a sign opposite to that of the Standard Model. Due to the importance of delayed decoupling in the hH+H− coupling, h→γγ improved measurements will have a strong impact on this issue. For the same reason, measurements or even bounds on h→Zγ are potentially interesting. In this article, we revisit this problem, highlighting the crucial importance of h→VV, which can be understood with simple arguments. We show that the impacts on kD<0 models of both h→bb¯ and h→τ+τ− are very sensitive to input values for the gluon fusion production mechanism; in contrast, h→γγ and h→Zγ are not. We also inquire if the search for h→Zγ and its interplay with h→γγ will impact the sign of the hbb¯ coupling. Finally, we study these issues in the context of the flipped two Higgs doublet model.

Estimation of rotational frequency response functions

As it is widely known, in structural dynamic applications, ranging from structural coupling to model updating, the incompatibility between measured and simulated data is inevitable, due to the problem of coordinate incompleteness. Usually, the experimental data from conventional vibration testing is collected at a few translational degrees of freedom (DOF) due to applied forces, using hammer or shaker exciters, over a limited frequency range. Hence, one can only measure a portion of the receptance matrix, few columns, related to the forced DOFs, and rows, related to the measured DOFs. In contrast, by finite element modeling, one can obtain a full data set, both in terms of DOFs and identified modes. Over the years, several model reduction techniques have been proposed, as well as data expansion ones. However, the latter are significantly fewer and the demand for efficient techniques is still an issue. In this work, one proposes a technique for expanding measured frequency response functions (FRF) over the entire set of DOFs. This technique is based upon a modified Kidder's method and the principle of reciprocity, and it avoids the need for modal identification, as it uses the measured FRFs directly. In order to illustrate the performance of the proposed technique, a set of simulated experimental translational FRFs is taken as reference to estimate rotational FRFs, including those that are due to applied moments.

Hydrogeomechanics for rock engineering: coupling subsurface hydrogeomechanical assessement and hydrogeotechnical mapping on fracturated rock masses

The present work aims to achieve and further develop a hydrogeomechanical approach in Caldas da Cavaca hydromineral system rock mass (Aguiar da Beira, NW Portugal), and contribute to a better understanding of the hydrogeological conceptual site model. A collection of several data, namely geology, hydrogeology, rock and soil geotechnics, borehole hydraulics and hydrogeomechanics, was retrieved from three rock slopes (Lagoa, Amores and Cancela). To accomplish a comprehensive analysis and rock engineering conceptualisation of the site, a multi‐technical approach were used, such as, field and laboratory techniques, hydrogeotechnical mapping, hydrogeomechanical zoning and hydrogeomechanical scheme classifications and indexes. In addition, a hydrogeomechanical data analysis and assessment, such as Hydro‐Potential (HP)‐Value technique, JW Joint Water Reduction index, Hydraulic Classification (HC) System were applied on rock slopes. The hydrogeomechanical zone HGMZ 1 of Lagoa slope achieved higher hydraulic conductivities with poorer rock mass quality results, followed by the hydrogeomechanical zone HGMZ 2 of Lagoa slope, with poor to fair rock mass quality and lower hydraulic parameters. In addition, Amores slope had a fair to good rock mass quality and the lowest hydraulic conductivity. The hydrogeomechanical zone HGMZ 3 of Lagoa slope, and the hydrogeomechanical zones HGMZ 1 and HGMZ 2 of Cancela slope had a fair to poor rock mass quality but were completely dry. Geographical Information Systems (GIS) mapping technologies was used in overall hydrogeological and hydrogeomechanical data integration in order to improve the hydrogeological conceptual site model.

Estratégias de planeamento de mobilidade ciclável e avaliação da transferência modal – caso de estudo em Almada

Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente, perfil de Ordenamento do Território e Impactes Ambientais

Influência dos tarifários de transportes colectivos na repartição modal dos transportes na AML

Dissertação para obtenção do Grau de Mestre em Engenharia do Ambiente, Perfil de Ordenamento do Território e Impactes Ambientais

Identificação modal e actualização de modelos de elementos finitos

Dissertação para obtenção do Grau de Mestre em Engenharia Civil - Perfil Estruturas

Coupling electrokinetics and iron nanoparticles for the remediation of contaminated soils

Fundação para a Ciência e a Tecnologia - PTDC/AGR-­AAM/101643/2008 NanoDC ; SFRH/BD/76070/2011 ; FP7-­PEOPLE-­IRSES-­2010-­269289-­ ELECTROACROSS

Identificação de dano estrutural com base em análise modal

O presente trabalho procura mostrar as potencialidades das técnicas de monitorização estrutural, de detecção, localização e caracterização de dano através de alterações dos parâmetros modais. As características dinâmicas de vibração de uma estrutura são alteradas pela presença de dano, o que, representando uma perda física, conduz à consequente perda de rigidez. Este fenómeno é responsável por modificações nas frequências naturais, deslocamentos modais e respectivas derivadas. Este trabalho apresenta a curvatura das configurações modais como possível parâmetro de controlo na identificação de dano estrutural. Neste documento encontram-se vários estudos de sensibilidade realizados em três modelos distintos (viga bi-apoiada, viga em consola e pórtico encastrado) em que se pretende avaliar a fiabilidade do método das curvaturas. Foram também desenvolvidos estudos respeitantes às alterações das frequências naturais e às alterações de dois indicadores estatísticos, o MAC e o COMAC. Com base nos resultados do método das curvaturas foi desenvolvida uma Java Applet, que constitui uma ferramenta de cálculo que permite explorar as potencialidades do método das curvaturas modais na identificação de danos em várias estruturas. Esta aplicação foi desenvolvida no compilador NetBeans IDE.

Análise modal de um edifício de paredes de alvenaria resistente

O parque habitacional em Portugal é composto por um elevado número de edifícios antigos constituídos por paredes de alvenaria resistente. Nos últimos anos tem-se constatado um interesse crescente na preservação e reutilização dessas construções, por se encontrarem frequentemente em zonas históricas privilegiadas, e com potencial interesse de exploração económica. Estes motivos têm levado à realização de intervenções estruturais nesses edifícios, com vista à reorganização dos espaços, podendo desencadear alterações no seu comportamento estrutural. O objetivo primordial deste estudo é avaliar as alterações da resposta modal de um edifício de paredes de alvenaria resistente, sujeito a uma intervenção de remoção das paredes num dos seus fogos. Para tal, realizaram-se duas campanhas experimentais de identificação modal à vibração ambiente, com o intuito de determinar as propriedades dinâmicas da estrutura, antes e após a intervenção. Procedeu-se à elaboração de um modelo de elementos finitos da estrutura recorrendo ao programa de análise de estruturas SAP2000, que permitiu efetuar também a correspondente análise numérica do problema. Foi ainda realizada uma análise ao comportamento modal do edifício, onde se identificaram diversas hipóteses que influenciam a resposta dinâmica da estrutura, tendo sido desenvolvidos alguns modelos numéricos, com o objetivo de examinar nomeadamente a influência dos edifícios adjacentes, e da interação solo-estrutura, no comportamento global do edifício analisado.

Coupling organic substrate removal to methane production in a fully biological microbial electrolysis cell

Microbial electrolysis cells (MECs) are an innovative and emerging technique based on the use of solid-state electrodes to stimulate microbial metabolism for wastewater treatment and simultaneous production of value-added compounds (such as methane). This research studied the performance of a two-chamber MEC in terms of organic matter oxidation (at the anode) and methane production (at the cathode). MEC‟s anode had been previously inoculated with an activated sludge, whereas the cathode chamber inoculum was an anaerobic sludge (containing methanogenic microorganisms). During the experimentation, the bioanode was continuously fed with synthetic solutions in anaerobic basal medium, at an organic load rate (OLR) of around 1 g L-1 d-1, referred to the chemical oxygen demand (COD). At the beginning (Run I), the feeding solution contained acetate and subsequently (Run II) it was replaced with a more complex solution containing soluble organic compounds other than acetate. For both conditions, the anode potential was controlled at -0.1 V vs. standard hydrogen electrode, by means of a potentiostat. During Run I, over 80% of the influent acetate was anaerobically oxidized at the anode, and the resulting electric current was recovered as methane at the cathode (with a cathode capture efficiency, CCE, accounting around 115 %). The average energy efficiency of the system (i.e., the energy captured into methane relative to the electrical energy input) under these conditions was over 170%. However, reactor‟s performance decreased over time during this run. Throughout Run II, a substrate oxidation over 60% (on COD basis) was observed. The electric current produced (57% of coulombic efficiency) was also recovered as methane, with a CCE of 90%. For this run the MEC‟s average energy efficiency accounted for almost 170 %. During all the experimentation, a very low biomass growth was observed at the anode whereas ammonium was transferred through the cationic membrane and concentrated at the cathode. Tracer experiments and scanning electron microscopy analyses were also carried out to gain a deeper insight into the reactor performance and also to investigate the possible reasons for partial loss of performance. In conclusion, this research suggests the great potential of MEC to successfully treat low-strength wastewaters, with high energy efficiency and very low sludge production.

Search for H→γγ produced in association with top quarks and constraints on the Yukawa coupling between the top quark and the Higgs boson using data taken at 7 TeV and 8 TeV with the ATLAS detector

A search is performed for Higgs bosons produced in association with top quarks using the diphoton decay mode of the Higgs boson. Selection requirements are optimized separately for leptonic and fully hadronic final states from the top quark decays. The dataset used corresponds to an integrated luminosity of 4.5 fb−1 of proton--proton collisions at a center-of-mass energy of 7 TeV and 20.3 fb−1 at 8 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess over the background prediction is observed and upper limits are set on the tt¯H production cross section. The observed exclusion upper limit at 95% confidence level is 6.7 times the predicted Standard Model cross section value. In addition, limits are set on the strength of the Yukawa coupling between the top quark and the Higgs boson, taking into account the dependence of the tt¯H and tH cross sections as well as the H→γγ branching fraction on the Yukawa coupling. Lower and upper limits at 95% confidence level are set at −1.3 and +8.0 times the Yukawa coupling strength in the Standard Model.