Comparação entre modelos constitutivos de interface: abordagem total versus abordagem com plasticidade

Nos últimos anos, a técnica de inserção de polímeros reforçados com fibras (FRP) no recobrimento de betão tem sido cada vez mais utilizada para reforçar estruturas de betão (técnica NSM). Este artigo apresenta os resultados obtidos em simulações numéricas de ensaios de arranque direto efetuados em cubos de betão reforçados com sistemas de FRP NSM. Duas estratégias diferentes são usadas para simular a interface entre o FRP e o betão envolvente. Uma estratégia baseia-se em expressões analíticas conhecidas a priori, enquanto a outra se baseia na teoria clássica de plasticidade com escoamento. Os resultados revelaram que ambas as estratégias são capazes de simular o comportamento global obtido nos ensaios de arranque

Lei constitutiva para a simulação da ligação de sistemas NSM FRP no betão

Nos últimos anos, a técnica de reforço NSM (Near-Surface Mounted) tem sido utilizada para aumentar a capacidade de carga de estruturas de betão. Esta técnica consiste na inserção de polímeros reforçados com fibras (FRP) no betão de recobrimento dos elementos estruturais. Normalmente, utilizam-se adesivos epóxidos como material de ligação entre o betão existente e o FRP a adicionar. Para estudar o comportamento da ligação em sistemas NSM FRP inseridos no betão é necessário ter em conta, não só o comportamento dos três materiais envolvidos (betão, FRP e o adesivo que os liga), mas também as duas interfaces existentes (FRP/adesivo e adesivo/betão). No caso dos três materiais envolvidos existem já leis constitutivas bastante robustas para modelar o seu comportamento. Contrariamente, ainda são escassas as leis constitutivas disponíveis para a modelação do comportamento das interfaces. Como consequência disso, a grande maioria dos trabalhos numéricos que existem na literatura ou consideram aderência perfeita entre materiais, não modelando por isso as interfaces, ou recorrem ao uso de leis “bond-slip” (definidas a priori e fisicamente questionáveis) para modelar as interfaces. Em alternativa, neste trabalho apresenta-se uma lei constitutiva baseada na teoria clássica da plasticidade com escoamento. Neste tipo de lei, o comportamento local da ligação é obtido a posteriori através do ajuste de um conjunto de parâmetros numéricos com significado físico bem definido. A lei referida foi implementada no software de elementos finitos FEMIX 4.0. As suas principais mais-valias prendem-se com a consideração dos modos de fratura I e II e ainda com a possibilidade de realizar modelações 2D ou 3D. A lei apresentada foi validada através da modelação de um ensaio de arranque direto em elementos de betão reforçados com sistemas NSM FRP. Os resultados obtidos mostram que a lei desenvolvida é adequada para a simulação das interfaces existentes nestes sistemas.Este trabalho foi apoiado por fundos nacionais através da FCT e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do Programa Operacional Fatores de Competitividade e internacionalização (POCI) e do Programa Regional de Lisboa no âmbito dos projetos FRPLongDur POCI-01-0145-FEDER-016900 (PTDC/ECM-EST/1282/2014) e POCI-01-0145-FEDER-00; primeiro autor gostaria também de agradecer a bolsa de doutoramento número SFRH/BD/87443/2012 concedida pela FCT e a bolsa de mobilidade concedida pelo projeto ‘‘EnCoRe” (FP7-PEOPLE-2011- IRSES No. 295283; www.encore-fp7.unisa.it) financiado pela união europei

Long-term management practices successfully reduce bird-related electrical faults in a transmission grid increasingly used by white storks for nesting

Bird nests on transmission lines can cause electrical faults which reduce service reliability. To address this problem, since the mid-90s, the Portuguese Transmission System Operator (TSO) has undertaken management actions to discourage white storks Ciconia ciconia from nesting in hazardous locations of the pylons. Here, we compiled and analyzed an 18-year series of data on electrical faults, TSO management actions to tackle these, and stork nests on transmission pylons in Portugal to: (a) determine the relative importance of bird-related faults over the total number of faults; (b) describe variations in bird-related faults across time (season of the year and time of the day); (c) describe spatial variations in bird-related faults and their association with the occurrence of white stork nests on pylons; and (d) analyze the trends, over the years, of the number of white stork nests on pylons, the TSO management actions and their effectiveness in reducing bird-related fault rates. Overall, birds accounted, on average, for 25.3% of the electrical faults in the transmission network, with the vast majority being attributed to white storks. The seasonal pattern of bird-related faults showed higher rates in April and in October–November. Faults occurred more often during the night period, when storks spend more time on the pylons. We found a positive spatial relationship between the electrical fault rate and the proportion of pylons with stork nests (and the correlated number of nests per 100 km of line). There was, however, considerable variation in the fault rates not explained by the stork nest variables, particularly during the non-breeding season. The TSO management actions (namely removal/translocation of nests in hazardous locations of the pylons, installation of anti-perching devices and provision of alternative nesting platforms) significantly reduced, as a whole, the annual number of bird-related faults between 2001 and 2018, despite the three-fold increase in the number of white stork nests on transmission pylons. A deeper understanding of how white storks use the transmission pylons outside the breeding season is needed, so that targeted management actions can be taken to reduce the remaining bird-related fault rates to residual levels.info:eu-repo/semantics/publishedVersio

Deduction of ultimate equilibrium limit states for concrete gravity dams keyed into rock mass foundations based on large displacement analysis

Concrete gravity dams are mass concrete structures, often built on rock mass foundations, conceived to rely upon their weight for stability. To prevent sliding, these structures are usually keyed/embedded into the foundation, a good construction practice particularly relevant in medium to high intensity seismic zones. In stability analysis, the extra strength obtained by keying the dam into the foundation is usually either neglected or taken as a passive resistance, which, such as explored in this paper, do not reflect the real structural response in pre-collapse situations. Limit state philosophy requires the ultimate equilibrium conditions to be expressed as accurately as possible. In this paper, the rigid-body equilibrium of a wedgy model representing the dam and a downstream rock wedge is analyzed according to the large displacement regime. Failure mechanisms were identified, analytically described and numerically validated. Application to two Portuguese large concrete gravity dams led to safety factors considerably larger than those computed assuming the usual practice. The proposed approach is intended to support probabilistic and/or semi-probabilistic methodologies for safety assessment of concrete gravity dams, in the design and feasibility phases, in which the limit state approach is inherently followed

Probabilistic model for the representation of the reservoir water level of concrete dams during normal operation periods

The dam’s reservoir water level varies over the year according to the water inflow and outflow, as a function of environmental events but also of dam exploitation management policy and human decisions. In the Portuguese dam safety regulation (RSB 2007), the normal water level (NWL) is considered as the optimum exploitation level. However, as proved by the continuous monitoring over the lifetime of a set of dams, the NWL is occasionally exceeded for non-negligible time periods. The reservoir water level, to which the water pressure on the upstream face is related, is a fundamental parameter for the safety and reliability analysis of concrete dams. When water-induced actions are considering the leading loads, only the maximum reservoir water level, usually associated with a high-return-period flood, is relevant. However, for other combinations, in particular, earthquake scenarios, the consideration of the variability of the water level over time is crucial. In reliability analysis of concrete dams, the reservoir water level has been considered either as a deterministic variable, once the loading scenario analyzed assume water-induced actions as leading loads (Westberg 2010), or as a random variable defined using hydrological site information of a specific study case (Altarejos et al. Structural Safety 36-37:1–13 2012). This work proposes a probabilistic model of the reservoir water level of any new dam based only on its geometrical properties, which provides a low-cost alternative to in-depth hydrological analysis. The proposed model can be useful in two stages of the lifecycle of dams: (i) initial design and feasibility stages, and (ii) routine safety assessment of existing structures, as in both stages the costs of a complete hydrological analysis is too high for the level of detail required. For that, the recorded reservoir water level of 27 Portuguese large concrete dams is used. A normalized sinusoidal model, with annual period, is adjusted to the reservoir water level annual history of those dams by beta regression. Generally, a good agreement between observations and the proposed model, for most of the annual adjustments, was achieved. The distribution parameters of the random variables were estimated through the maximum likelihood estimation (MLE) method. The physical, model and statistical uncertainties were quantified and can now be included in a reliability analysis procedur

Interactions lake-atmosphere: The ALEX 2014 field campaign and numerical simulations

The ALqueva hydro-meteorological EXperiment, ALEX 2014, was an integrated field campaign with measurements of chemical, physical and biological parameters in water and air at different experimental sites in the region of the Alqueva reservoir, a 250 km2 man made lake, in the southeast of Portugal. The Field campaign took place from June 1 to September 30, 2014 and comprises an Intensive Observation Period (IOP) of three days (22 to 24 July). During the four months, the over water fluxes of momentum, heat and mass (H2O and CO2) were obtained with an integrated Open-Path CO2 /H2O Gas Analyser and 3D Sonic Anemometer, mounted on a floating platform, where radiative fluxes were also measured, as well as the water temperature profile. Eight near surface weather stations were operating in the area and air quality, atmospheric electrical field (Potential Gradient) and radon (222Rn) concentration were continuous monitored. Along this period, in situ measurements, water samples and biological elements were monthly collected from three fixed platforms placed in the lacustrine zone and from selected sites in the margins. During the IOP, radiosondes were launched every tree hours, allowing a characterization of the atmospheric boundary layer and its evolution. In 10 occasions Geigersondes were coupled to the radiosondes in order to obtain the atmospheric ionization profile. The boundary layer was characterized with a Ceilometer and the vertical distribution of O3 and NO2 were obtained from a Spectrometer. A GPS network of 15 GNSS stations was installed in order to map the water vapour. The sky brightnesson the nights of July 24 and 25, was measured using a Sky Quality Meter. The lake-atmosphere interactions and its impact in the boundary layer structure and in the local circulations are studied using data collected during the ALEX 2014 POI together with results from numerical simulations performed with the non-hydrostatic Meso-NH french model

Adaptação para português europeu do Brief Jail Mental Health Screen, do Correctional Mental Health Screen e do Modified Simple Screening Instument for Substance Abuse

Os objetivos da presente investigação consistem na tradução para português europeu de três instrumentos de rastreio da saúde mental e validação à população reclusa portuguesa. Vários estudos efetuados em Estabelecimentos Prisionais são unanimes em referir que, em relação à comunidade em geral, a doença mental na população reclusa está sobre representada (Brink, Doherty, & Boer, 2001; Fazel & Seewald, 2012; Ford & Trestman, 2005; Martin, Colman, Simpson, & McKenzie, 2013; Steadman, Osher, Robbins, Case, & Samuels, 2009; Teplin, 1990), o que estabelece um desafio às instituições prisionais, lidar com o influxo de sujeitos que entram no sistema já com sintomatologia patológica enquanto implementam medidas de controlo e manutenção da ordem prisional. Os instrumentos selecionados incluem as perturbações mentais mais associadas à população reclusa, o MSSI-SA é composto por 16 itens e avalia o abuso e dependência de AOD, o BJMHS é composto por oito itens e é válido para perturbações da esquizofrenia, bipolaridade e depressão major e o CMHS-M/W tem versões distintas para o género, com 8 e 12 itens (mulheres e homens, respetivamente) e está validado para a depressão, ansiedade, PSPT, algumas desordens de personalidade, ou qualquer outra doença mental encoberta. A interpretação dos resultados obtidos nesta investigação permite inferir que as versões experimentais apresentam critérios de consistência interna ajustados para a população reclusa portuguesa, sendo o valor de ? para a escala feminina, escala masculina e escala completa o seguinte: para o MSSI-SA o resultado foi 0.94, 0.96 e 0.95, respetivamente, para o BJMHS foi 0.64, 0.64 e 0.61, respetivamente, para CMHS-W (escala feminina) foi 0.83 e para o CMHS-M (escala masculina) foi 0.79. Verifica-se uma correlação positiva e estatisticamente significativa entre os scores do BJMHS e do CMHS-W/M, tendo sido para mulheres e homens, [r (72) = .74, p < .001] e [r (116) = .69, p < .001], respetivamente, o que permite inferir que apresentam validade de critério concorrente. O cruzamento entre a informação prestada pelos entrevistados e o ponto de corte dos instrumentos de rastreio da saúde mental permitiu identificar que tanto o MSSI-SA como o BJMHS referenciaram todos os sujeitos diagnosticados nos serviços prisionais por abuso ou dependência de AOD e perturbação mental, respetivamente, já no CMHS-W a percentagem de falsos negativos foi 4.2% e no CMHS-M foi 5.2%. Em suma, o análise estatística inferencial dos resultados permitem interpretar que os três instrumentos breves de rastreio da saúde mental estão ajustados para a população reclusa portuguesa, no entanto, futuras investigações deverão incidir no apuramento dos falsos negativos e falsos positivos por meio de entrevistas de diagnóstico de acordo com os critérios do DSM-V ou do CID-10.The aim of this research consist in the translation into European Portuguese of three screening instruments of mental health and validation to the Portuguese prison population. Several studies conducted in Prisons are unanimous in noting that, in relation to the wider community, the mental illness in the prison population is over represented (Brink et al., 2001; Fazel & Seewald, 2012; Ford & Trestman, 2005; Martin et al., 2013; Steadman et al., 2009; Teplin, 1990), which sets a challenge to correctional institutions to cope with the influx of individuals who enter in the system already with pathological symptoms while implementing control measures and maintaining prison order. The selected instruments include mental disorders more associated with the prison population, the MSSI-SA consists of 16 items and it assesses the abuse and dependence on AOD, the BJMHS consists of eight items and is valid for disorders of schizophrenia, bipolar disorder and major depressive disorder and CMHS-M/W has different versions for the gender, with 8 and 12 items (women and men, respectively) and is validated for depression, anxiety, PTSD, some personality disorders, or the presence of any undetected mental illness. The interpretation of the results obtained in this research allows to infer that the trial versions have internal consistency criteria set for the Portuguese prison population, and the value of ? for the female scale, male scale and full scale as follows: for the MSSI-SA results was 0.94, 0.96 and 0.95, respectively, for BJMHS was 0.64, 0.64 and 0.61, respectively, for CMHS-W (female scale) was 0.83 and the CMHS-M (male scale) was 0.79. There is a positive and statistically significant correlation between the scores of BJMHS and CMHS-W/M, being for women and men, [r (72) = .74, p <.001] and [r (116) = .69, p <.001], respectively, which allows to infer that they have concurrent validity. The cross between the information provided by the interviewed and the cutoff of mental health screening tools allowed to identify that both the MMSI-SA and BJMHS have referred all diagnosed subjects in the prison services for abuse or dependence on ODA and mental disturbance, respectively; however, in W-CMHS the percentage of false negatives was 4.2%, and in CMHS-M it was 5.2%. In sum, the inferential statistical analysis of results allows to interpret that the three brief instruments of mental health screening are set for the Portuguese prison population, however, future research should focus on the clearing of false negatives and false positives through diagnostic interviews according to the DSM-V and ICD-10 criteria

Optimization of geometry and performance of cooling bundles of parallel tubes with pumping power requirements

This study provides answers the following question: what is the best geometry for a required level of the heat exchange, taking into account the fluid pumping power? This study shows that there exists a minimum of the fluid pumping power for the optimal heat exchanged along a stream network composed by a bundle of parallel tubes. This optimization opportunity was applied to networks under laminar and turbulent flow regime

Performance analysis of an endoreversible heat pump system for optimal air–ground or water environmental exergy potential utilization

This paper reports the optimization of a ground or water source heat pump system for housing applications with respect to the best exergy performance and maximum environmental exergy potential use. The analysis presented also offers the opportunity of exploring a new objective for the optimization of the use of exergy sources: ‘In any system powered by an external exergy source optimization is achieved when the exergy flux to the environment is minimum under the existing constraints’. This corresponds to utilizing the supplied exergy to overcome the total irreversibilities of such a system only. The environmental exergy utilization and the exergy output to the environment are analyzed in connection with this objective

Exergy Analysis and Optimisation of a Ground or Water Source Heat Pump System for Maximum Environmental Exergy Potential Utilisation

This paper presents the exergy analysis and optimisation of a ground or water source heat pump system for housing applications with the purpose of best performance and maximum environmental exergy potential use. The present analysis also offers the opportunity of defining a new objective function for the optimisation of the use of exergy sources: 'In any system powered by an external exergy source optimisation is achieved when the exergy flux to the environment is minimum under the existing constraints”. This corresponds to utilizing the available exergy to overcome the total irreversibilities of such a system only. The environmental exergy utilisation and the exergy output to the environment are analysed in relation with this objective