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Assessing the Quality of an UAV-based Orthomosaic and Surface Model of a Breakwater
No full textThe low price and the quality of the products derived from photographs taken by cameras mounted on unmanned aerial vehicles (UAV) turn them very attractive to be used in several situations, namely when the area that needs to be covered hasn’t a large extension or when is necessary to have data, like coordinates of points, on a periodic basis. The monitoring of the behavior of breakwaters fall is this category of works. Usually with extensions of some hundred meters long, with only a few meters high and with long flat surfaces, breakwaters are structures with a shape very attractable to be monitored by unmanned airplanes and helicopters. The National Laboratory for Civil Engineering, from Portugal, responsible by the evaluation of new methodologies and techniques applied to the monitoring of large civil engineering structures like dams, bridges, buildings and breakwaters, has been testing the use of an unmanned small airplane in the monitoring of a 400 m long breakwater. The first stage of the work was to assess the quality of the surface model built with the use of photographs taken by a small digital camera mounted on an UAV. By comparing coordinates of selected points extracted from the digital surface model, build with images taken at an average altitude of 185 m, with coordinates derived from GNSS high quality observations, it was obtained differences of 10 cm (root mean square error) in planimetry and 8 cm in height. This paper describes the conditions of the UAV flight and of the breakwater environment, conditions that were particularly hard, and presents the results of the quality control of the surface model, made with the use of statistical methods.15516DBB/NGA201416 a 21 de junh
Efeitos estruturais das sobrecargas rodoviárias definidas nas normas mais utilizadas pela engenharia portuguesa em tabuleiros de betão com secção em caixão
No full textAs ações verticais em tabuleiros de pontes rodoviárias têm sido definidas, em Portugal, considerando o Regulamento de Segurança e Ações para Estruturas de Edifícios e Pontes (RSA), mas num futuro próximo prevê-se a utilização do Eurocódigo 1 (EC1). Porém, a engenharia de pontes portuguesa tem vindo a envolver-se, nos últimos anos, no projeto e construção de obras nos continentes africano e americano, onde vigoram outras normas. Assim, atendendo aos diferentes regulamentos que o meio técnico nacional tem que usar, realizou-se um estudo comparativo dos efeitos estruturais devidos aos modelos de sobrecargas rodoviárias de cinco normas, designadamente o RSA, o EC1, a norte--americana AASHTO, a sul-africana SATCC e a brasileira ABNT, em tabuleiros de betão de grande vão com secções em caixão, com o objetivo de fornecer indicações úteis aos projetistas e construtores. Os resultados obtidos permitiram concluir que, na direção longitudinal, a ABNT é mais condicionante, ao passo que o EC1 induz esforços mais gravosos na direção transversal. Para os tabuleiros mais largos e de maior vão, o RSA pode ter efeitos mais desfavoráveis que o EC1, na direção longitudinal.16pDBB/CHEFI
Avaliação do risco de galgamentos e inundação: integração de um método expedito de inundação no sistema HIDRALERTA
No full textO HIDRALERTA é um sistema de previsão, alerta e avaliação do risco associado aos galgamentos e inundação em zonas portuárias, tendo como ideia-base a utilização de medições/previsões da agitação marítima para calcular o galgamento e a inundação nessas zonas. A avaliação do risco associado a estes fenómenos é efetuada através da definição de limiares para os caudais galgados ou para as cotas de inundação admissíveis, e pelo produto do grau da probabilidade de ocorrência de valores desses caudais pelo grau das consequências desses acontecimentos.
No sistema, o cálculo dos caudais médios galgados sobre uma estrutura é efetuado com recurso a ferramentas neuronais (NN_OVERTOPPING2) e/ou ferramentas empíricas, que são métodos expeditos e que não fornecem indicação sobre a distribuição espacial desse caudal na zona atrás da estrutura.
Nesta comunicação, é apresentada uma metodologia incorporada no HIDRALERTA com o intuito de modelar o galgamento e a inundação na sua distribuição espacial, recorrendo a ferramentas SIG. Essa metodologia consiste na utilização dos resultados da NN_OVERTOPPING2 para o cálculo do caudal médio galgado por metro linear de estrutura, a partir de onde se pode obter o volume de água correspondente e posterior distribuição desse volume no modelo Digital do Terreno da zona em estudo. O caso de estudo localiza-se no porto e baia da Praia da Vitória, na Ilha Terceira, nos Açores.431-436ppDHA/NP
Combined Use of Electrical Resistivity Tomography and Hydrochemical Data to Assess Anthropogenic Impacts on Water Quality of a Karstic Region: A Case Study from Querença-Silves, South Portugal
No full textThe presence of highly vulnerable karstic systems in areas of intense human
activities often results in the degradation of existing surface- and groundwater quality
status. Water quality protection and improvement, as required by the Water Framework
Directive (WFD), depends on correct identification and prioritisation of the most
relevant pollution sources within complex multi-stressor conditions. This paper presents
a methodology that combines the use of hydrogeology, water quality and
quantity data, and electrical resistivity tomography methods to access different anthropogenic
impacts upon the water cycle, focusing on the water quality of a section of
the Portuguese karstic Querença-Silves aquifer. During this study an interpretation of
the possible interconnections between pollutant sources, their pathways and local
surface-groundwater connections was made, based on data obtained from field campaigns.
As a result of this study, the areas with more interconnection between surfaceand
groundwater were identified, namely the influent sites from the local stream into
the aquifer. The impact of the diffuse pollution sources was verified at the monitoring
points, especially those located downstream of large farming plots. Pollution in this
karst aquifer results from seepage through agricultural areas and infiltration at the
influent points of the stream. This aspect of stream influence upon the aquifer means
that pollution sources located upstream of the area of the aquifer (e.g., a WWTP—
Wastewater Treatment Plant) can also contribute to the aquifer pollution.15DHA/NR
Connection for round wood timber members using multiple glued-in rods
No full textThis paper presents a research work undertaken, whose main purpose was the development and validation of an innovative connection system for round wood members. The connection proposed is based on axially glued-in rods. A preliminary research was undertaken in order to assess the properties of the glued-in rods using different gluing lengths, steel grades and timber densities. Based on these results three connection configurations were defined aiming the optimization of the connection load carrying capacity. These configurations were afterwards tested in laboratory to assess their mechanical performance. The results obtained showed that the proposed connection leads to high performance, either in terms of load carrying capacity or stiffness if appropriate connection configurations are used.7ppSeminário / World Conference on Timber Engineering, WCTEDE/NC
Zonas domésticas: propostas organizativas – I
No full textTrata-se de um relativo culminar de toda uma tradição de zonamentos funcionais ou funcionalistas, zonamentos estes que, infelizmente, ajudaram a destruir bairros de cidades e a uniformizar espaços domésticos no sentido do serviço a uma pessoa “média” e a uma família “média”, provavelmente a tal que deseja o T3, mas que acaba por se contentar com um T2 com uma pequena sala e uma pequena cozinha, quartos dimensionados para “mobílias completas” e uma sala-comum onde quase nem há espaço para encaixar todo o catálogo de mobiliário, quanto mais para aceitar toda uma vida doméstica que aí se tem de concentrar.1 fig4 pInfohabitar, Ano X, n.º 492DED/NUTRevista Infohabita
Cost-Benefit Analysis of Future Vehicle Technologies: exploring electric vehicle sharing schemes and intermodality in Lisbon.
No full textThis paper presents a comparative cost-benefit analysis of future vehicle technologies and electric mobility services until 2030 for the case of Lisbon Metropolitan area (LMA). The roles of electric vehicles (car, scooter and bike sharing) along with intermodal transport (train and underground) are explored as a means to improve the sustainability of the passenger transport sector. The methodology considered a life-cycle assessment of Battery-powered Electric Vehicles (BEVs) and Internal Combustion Engine Vehicles - gasoline (ICEVs), taking the perspective of the user, in terms of CO2 and energy consumption. The analysis covered emissions along the entire chain of production and usage of vehicles – the Well-to-Wheel (WtW) analysis, comprising the Well-to-Tank (WtT) and the Tank-to-Wheel (TtW) emissions, where the energy grid trend scenarios (mix of electricity production) explored the incorporation of renewable for emissions’ reduction (gCO2/kWh).Fundação para a Ciência e Tecnologia e LNEC.1810O artigo completo foi elaborado (e submetido) em 2013 no âmbito do projeto financiado pela FCT COST-TRENDs coordenado pela Eng.ª Elisabete Arsenio.DT/NPTS201414 a 17 de Abri
A tool for a comprehensive assessment of treated wastewater quality
No full textThe main goal of a wastewater treatment plant (WWTP) is to comply with the treated wastewater
(TWW) quality requirements. However, the assessment of this compliance is a rather complex process
for WWTPs in the EU Member States, since it requires the integration of a large volume of data and
several criteria according to EU Directives 91/271/EEC and 2000/60/EC. A tool for a comprehensive
assessment of TWW quality in this context is herein presented. The tool's novelty relies on an integrated
analysis of performance indicators (PIs) and new performance indices (PXs). PIs integrate the several
compliance criteria into a single framework, supported by flowcharts for a straightforward assessment of
TWW compliance by practitioners. PXs are obtained by applying a performance function to the con-
centration values analysed in the TWW for discharge or reuse. PXs are dimensionless and the scale
adopted (0e300) defines three performance levels: unsatisfactory, acceptable and good performance.
The reference values proposed for these levels and for the PIs were based on the EU legislation. The PXs
complement the information provided by the PIs. While the latter assess the plant effectiveness in a
given year (i.e. the TWW compliance with the requirements), PXs tackle the plant reliability, i.e. they
allow to easily compare the performance of different parameters over the time and to identify when the
performance did satisfy or fail the pre-established objectives and the distance that remains to achieve
these targets. The tool was tested in 17WWTPs and the most representative results are herein illustrated.727p146DHA/NESJornal of Environmental Managemen
Complementary spillway of Salamonde dam. Physical and 3D numerical modelling
No full textThroughout the planning and design of hydraulic structures, engineers and researchers are
increasingly integrating computational fluid dynamics (CFD) into the process. Despite reports
of success in the past, there is still no comprehensive assessment that assigns ability to CFD
models to simulate a wide range of different spillways configurations.
The complementary spillway of Salamonde dam, located in the north of Portugal, is controlled
by an ogee crest and two radial gates, followed by a free surface flow tunnel, with a rather
complex geometry, and a terminal ski jump which directs the jet into the river bed. The present
paper analyses the ability of a CFD model (FLOW-3D) to simulate the flows along this
spillway.
The spillway was primarily tested and developed in a physical model built in the National
Laboratory for Civil Engineering (LNEC), where discharges and flow depths were measured in
ten defined cross-sections for four different gate openings conditions. These results were used
to calibrate the numerical model and to analyze the differences between physical and
numerical models results.
It is shown that there is an accurate agreement between physical and numerical model
discharges. Concerning the flow depths, the FLOW-3D represents reasonably well the flow
behavior, but slightly underestimates the flow depth in some points of the cross-sections. A
sensitivity analysis for the conditions and parameters of the numerical model (e.g., 1st vs 2nd
order momentum advection, turbulent mixing length TLEN, mesh size) was carried out.
According to FLOW-3D results, for a certain reservoir level, spillway discharge and flow depth
are highly dependent on mesh size.
Conclusions about the most adequate FLOW-3D options to adopt are presented. The calibrated
model was used to simulate the spillway design discharge and to assess the hydraulic behavior
of the outlet structure and of the jet impingement characteristics. The pressure distribution in
specific cross-sections was also assessed.ISBN 978-989-96479-2-3DHA/NRE201414 a 16 de abri
Wave interaction with a vertical wall: SPH numerical and experimental modeling
No full textPrediction of wave forces on caisson-type breakwaters is challenging, especially in the case of impact loads that strongly depend on wave reflection, and wave breaking which affects the wave characteristics near the structure. In recent years, numerical models have been further developed and their use is becoming increasingly attractive, such as the Smoothed Particle Hydrodynamics (SPH) numerical models which enable the simulation of complex free surface flows. The SPH numerical model developed at the National Laboratory for Civil Engineering (LNEC) is validated by comparing the numerical results of the wave interaction with a vertical wall using data obtained from physical modeling tests carried out in one of the LNEC׳s flumes. The numerical results presented a good agreement with the physical model tests. The free surface level was well estimated, with a concordance index between numerical results and experimental data of about 90.5–99.1%, presenting an average value of 95.5%. Pressure at the vertical wall shows high intensity and short duration impact loads, and presented a concordance index between numerical results and experimental data about 68.8–94.4%, with an average value about 86.2%. Considering the complex phenomena involved, which is highly difficult to be accurately modeled, numerically and experimentally, a good agreement between physical tests and numerical results was accomplished.1314330–341ppVol. 88DHA/NPEOcean Engineerin