ESTGV - DEC - Artigo em revista científica, não indexada ao WoS/Scopus
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- Air permeability measurements of dwellings and building components in PortugalPublication . Pinto, Manuel; Viegas, João; Freitas, VascoVentilation represents a significant part of heat loss in winter, leading to the need to minimize airflow. However, it is absolutely necessary to ensure indoor air quality and the safety of the users and to control the risk of condensation. Ventilation is responsible on average for 30%e40% of energy consumption in air conditioning in Western European buildings. There is great variability in air change rates (ACH [h 1]) from country to country and the minimum value takes into account comfort, sensory and hygrothermal criteria. In Portugal improvements have been made in the air permeability of window frames, but despite the improvements also made in installing mechanical extraction ventilation devices in kitchens and toilets, these often do not guarantee the minimum number of air change rates required. Air permeability tests were recently carried out in five flats with identical construction characteristics, in the same building, with the aim of characterizing the air permeability of buildings and components, in Portugal. These data are particularly useful for improving the design of building components (e.g., windows and roller shutter boxes) and to perform simulations with reliable data.
- Calibration of the Gipps Car-following Model Using Trajectory DataPublication . Vasconcelos, Luís; Neto, Luís; Santos, Sílvia; Bastos Silva, Ana; Seco, ÁlvaroOne of the most important tasks in the microscopic simulation of traffic flow, assigned to the car following sub-model, is the modelling of the longitudinal movement of vehicles. The calibration of a car-following model is usually done at an aggregated level, using macroscopic traffic stream variables (speed, flow, density). There is an interest in calibration procedures based on disaggregated data. However, obtaining accurate trajectory data is a real challenge. This paper presents a low-cost procedure to calibrate the Gipps car-following model. The trajectory data is collected with a car equipped with a datalogger and a LIDAR rangefinder. The datalogger combines GPS and accelerometers data to provide accurate speed and acceleration measurements. The LIDAR measures the distances to the leading or following vehicle. Two alternative estimation methods were tested: the first follows individual procedures that explicitly account for the physical meaning of each parameter; the second formulates the calibration as an optimization problem: the objective function is defined so as to minimize the differences between the simulated and real inter-vehicle distances; the problem is solved using an automated procedure based on a genetic algorithm. The results show that the optimization approach leads to a very accurate representation of the specific modeled situation but offers poor transferability; on the other hand, the individual estimation provides a satisfactory fit in a wide range of traffic conditions and hence is the recommended method for forecasting purposes.
- Capacity of normal and turbo-roundabouts: comparative analysisPublication . Vasconcelos, Luís; Silva, Ana Bastos; Seco, ÁlvaroWhile researchers agree as to the safety benefits of turbo roundabouts, their improvements in terms of capacity and delay remain open to discussion. This is mostly because previous research is based on capacity models that do not fully describe the complex interactions between the traffic streams on multilane roundabouts. This paper proposes a procedure to calculate capacity based on gap-acceptance theory. It addresses the limitations mentioned by accounting for usually disregarded effects such as the dynamic choice of the entry lane and unequal allocation of traffic in the circulatory lanes. Capacities were calculated for a wide range of demand scenarios and it has been shown that only under demand scenarios that are very specific and uncommon in real world networks, associated with very high percentages of rightturning entry traffic, can a standard turbo roundabout be expected to provide more capacity than the equivalent two-lane roundabout. It has also been shown that two lane roundabouts can normally be expected to provide capacities 20 to 30% above those of comparable turbo roundabouts.
- Caracterização Experimental de um Sistema de Ventilação Misto em Edifícios de HabitaçãoPublication . Pinto, Manuel; Freitas, VascoDevido à variação de factores naturais, nomeadamente a direcção e a velocidade do vento e a flutuação da temperatura, os sistemas de ventilação natural nem sempre permitem assegurar as taxas de renovação horária ideais. Para isso consideramos fundamental caracterizar o funcionamento de um sistema de ventilação misto (entradas de ar auto-reguláveis nos quartos e salas, extracção natural nas instalações sanitárias e exaustão mecânica na cozinha) que poderá contribuir para uma estratégia de ventilação de grande interesse. O estudo pretende avaliar qual a melhor constituição de um sistema misto de ventilação e definir regras construtivas a implementar de modo a permitirem alcançar as renovações horárias preconizadas na normalização e regulamentação portuguesa.
- Comparison of procedures to estimate critical headways at roundaboutsPublication . Vasconcelos, Luís; Seco, Álvaro; Silva, Ana BastosThe capacity analysis of roundabouts in Portugal is mostly done using the UK regression method. Due to its empirical and non-explanatory nature, this method has some limitations, particularly for studying innovative layouts, which has recently motivated research in Portugal into the use of capacity methods based on gap-acceptance theory. This paper describes the results of a related project: the estimation of critical headways and follow-up times at Portuguese roundabouts. For this study, gap-acceptance data were collected at six roundabouts, in two cities, and used to estimate the parameters at each entry, for the left and right entry lanes independently. Several estimation methods were used (Siegloch, Raff, Wu, Maximum Likelihood and Logit). The results have revealed important specificities of the methods that have significant effects on the results and therefore on the capacity estimate exercises. The comparison of the estimates with reference values from several countries indicates significant differences, suggesting the existence of relevant driving style differences, which implies that locally calibrated, country-specific, parameters are required for capacity calculations.
- Estimating the Parameters of Cowan’s M3 Headway Distribution for Roundabout Capacity AnalysesPublication . Vasconcelos, Luís; Silva, Ana Bastos; Seco, Álvaro; Silva, João PedroCapacity models based on the gap acceptance theory are widely used in unsignalised intersections and roundabout capacity analysis. These models are based on the statistical distribution of major vehicle headways. In this field, Cowan’s M3 distribution is usually recognized as the most adequate, but the estimation of its parameters is not trivial. In this paper, the main estimation methods are reviewed and a new method (Simultaneous Numerical Estimation – SNE) is proposed. The SNE method was used to develop a calibrated relation between parameters, using field data collected in Portuguese roads and roundabouts. It was determined that the new formula improves capacity estimates, either in one-lane or in two-lane roundabouts. The paper also addresses the importance of each input variable and parameter in the resulting capacity model, through a sensitivity analyses.
- Experimental assessment of IAQ improvement in naturally ventilated educational buildingsPublication . Pinto, Manuel; Almeida, Ricardo; Pinho, Paulo; Lemos, Luís; Lanzinha, JoãoIndoor environmental conditions in classrooms, in particular temperature and indoor air quality, influence students’ health, attitude and performance. In recent years several studies regarding indoor environmental quality of classrooms were published and natural ventilation proved to have great potential, particularly in southern European climate. This research aimed to evaluate indoor environmental conditions in 8 schools and to assess their improvement potential by simple natural ventilation strategies. Temperature, relative humidity and carbon dioxide concentration were measured in 32 classrooms. Ventilation performance of the classrooms was deeply characterized by tracer gas measurements of the air change rate assuming different windows related boundary conditions. A total of 110 tracer gas measurements were made. The complete characterization of the classrooms ventilation performance was relevant for the definition of the ventilation protocol since air change rate helped to pinpoint the best ventilation strategy for each case study. The results of the ventilation protocol implementation were very encouraging and, globally, a significant decrease on the CO2 concentration was observed without modifying the comfort conditions. This paper presents and discusses the main conclusions of the measurements campaign performed in the referred classrooms.
- Indoor environmental quality of classrooms in Southern European climatePublication . Almeida, Ricardo; Freitas, VascoThe indoor environmental quality within a classroom is linked to the health, comfort and performanceof students. It is well established that there are classroom environments where indoor environmentalquality is poor. Therefore, the rehabilitation of school buildings is assumed as an appropriate strategy.Consequently, some countries have sponsored nationwide programs for the rehabilitation of school build-ings, whose result has been, in some cases, other than the expected. Classrooms performance in serviceconditions must be evaluated and, from the results, optimized solutions should be established and care-fully designed and executed to have the desired effect. Thus, a research project was defined, aiming toassess the impact of retrofit on the indoor environmental quality of school buildings. The methodologyused included the in situ measurement of temperature, relative humidity, carbon dioxide concentrationand ventilation rates. A total of 24 classrooms of 9 school buildings (2 non-retrofitted and 7 recentlyretrofitted) were studied. A long term monitoring was defined with three measurement campaigns:winter, mid-season and summer conditions, each with three weeks length. The results confirmed thatnon-retrofitted schools need to improve their indoor environmental conditions and in retrofitted build-ings mechanical ventilation systems are not being used, with important consequences on the indoor airquality.
- Modelos Preditivos para Ventilação NaturalPublication . Pinto, Manuel; Silva, Fernando; Freitas, VascoA noção de desenvolvimento implica necessariamente a melhoria das condições de vida das populações, ou seja, conforto entendido em sentido lato incluindo, por exemplo, a Qualidade do Ar Interior. O recurso a sistemas AVAC para garantir as condições de conforto tem algumas desvantagens, nomeadamente o recurso a energias primárias finitas. Está hoje generalizada a ideia de que a Energia e o Ambiente são bens que têm de ser geridos e utilizados com os cuidados devidos ao que é finito. No sentido de incrementar o recurso a energias renováveis, infinitas por definição e não poluentes, apresentam-se no presente artigo modelos preditivos para ventilação natural que recorrem a duas fontes: as diferenças de temperatura exterior-interior e o vento. Estes modelos podem ser usados na fase de concepção arquitectónica para prever as renovações horárias devido à existência de aberturas na envolvente de edifícios, por exemplo em edifícios de serviços ou comerciais.
- Natural ventilation and indoor air quality in educational buildings: experimental assessment and improvement strategiesPublication . Almeida, Ricardo; Pinto, Manuel; Pinho, Paulo G.; Lemos, Luís T. deIndoor environmental conditions in classrooms, in particular temperature and indoor air quality, influence students’ health, attitude and performance. In recent years, several studies regarding indoor environmental quality of classrooms were published and natural ventilation proved to have great potential, particularly in southern European climate. This research aimed to evaluate indoor environmental conditions in eight schools and to assess their improvement potential by simple natural ventilation strategies. Temperature, relative humidity and carbon dioxide concentration were measured in 32 classrooms. Ventilation performance of the classrooms was characterized using two techniques, first by fan pressurization measurements of the envelope airtightness and later by tracer gas measurements of the air change rate assuming different envelope conditions. A total of 110 tracer gas measurements were made and the results validated ventilation protocols that were tested afterward. The results of the ventilation protocol implementation were encouraging and, overall, a decrease on the CO2 concentration was observed without modifying the comfort conditions. Nevertheless, additional measurements must be performed for winter conditions.