Elisabete Freitas
Universidade do Minho, Civil Engineering, Faculty Member
- Dr. Elisabete Fraga de Freitas holds a BSc and Ph.D. in Civil Engineering from the University of Minho. She is Resear... moreDr. Elisabete Fraga de Freitas holds a BSc and Ph.D. in Civil Engineering from the University of Minho. She is Researcher and Assistant Professor in Civil Engineering Department of that university since 1998. She develops research on surface characteristics of road pavements, including new surface functions, and road safety. The present main areas of work are the investigation of tire/pavement interaction, particularly the analysis of its effect on annoyance, vehicle detection, and pedestrian´s behaviour, photocatalic, self-cleaning and anti-ice pavement surfaces, and also investigation of accident factors, accident modelling, and pedestrian behaviour, addressing the field, laboratory (experimental and simulation), and numerical components. She has been involved in several funded research national and international projects, as principal researcher and member in those areas, e.g. Nanoecobuild - Nanotechnology-based concepts applied to innovative and eco-sustainable building material surfaces (PTDC/FIS/120412/2010); “Noiseless - Noise perception, modelling and abatement using innovative and durable pavement surface layers” (PTDC/TRA/67859/2006); “AnPeB - Analysis of pedestrians’ behaviour based on simulated urban environments and its incorporation in risk modelling” (PTDC / ECM -TRA / 3568/2014). She participated in the organization of several conferences, and she is the author of more than 110 papers in international and national journals and conferences. She is a member of the editorial board of the journal “Transportation Research - Part D and expert member of the Working Group CEN / TC 227 / WG 5 and coordinator of the mirror Sub-Committee.edit
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With the pressure to lower traffic noise limits due to environmental impacts, many questions have been raised regarding pedestrians’ safety. Aiming at investigating the effect of traffic noise on crossing behaviour of pedestrians, a... more
With the pressure to lower traffic noise limits due to environmental impacts, many questions have been raised regarding pedestrians’ safety. Aiming at investigating the effect of traffic noise on crossing behaviour of pedestrians, a virtual environment was reproduced based on data collected from a vehicle passing-by at different speeds and decelerations. In the virtual environment, an experiment with nineteen auditory stimuli was carried out. Eleven participants were asked to signal the moment they thought it was safe to cross the street, without visual information about the car approaching. The Time-to-Collision (TTC) was calculated and compared to the real TTC, to assure that pedestrians’ real vs. virtual crossing behaviour was identical. Afterwards, the crossing rate was calculated and correlated with acoustic and psychoacoustic parameters. Loudness was found to be the best indicator for representing the crossing rate, followed by the maximum sound pressure level (SPLmax). Withou...
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Pavement’s surface condition is a key parameter to evaluate traffic safety because it directly characterizes friction levels, related to the quality of vehicular braking. Defined by both microand macrotexture, different techniques applied... more
Pavement’s surface condition is a key parameter to evaluate traffic safety because it directly characterizes friction levels, related to the quality of vehicular braking. Defined by both microand macrotexture, different techniques applied to determine skid resistance are documented in the literature. In order to standardized skid resistance, International Friction Index (IFI) was developed. Its main goal is to quantify frictional coefficient, reporting it as a single-scale indicator, which can be assessed worldwide. In this context, this paper’s mean objective is to assess skid resistance for different paving techniques. For that, an extent database of microand macrotexture was collected from the literature, counting on more than 10 different paving techniques. From this analysis, curves of frictional coefficient versus speed were plotted, observing macrotexture’s preponderance on skid resistance performance. Key-words: surface condition, skid resistance, International Friction Inde...
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Transportation noise is considered today a major environmental risk factor and an important public health issue, especially in urban settings. Road, railway, and aircraft transports can produce high levels of continuous or intermittent... more
Transportation noise is considered today a major environmental risk factor and an important public health issue, especially in urban settings. Road, railway, and aircraft transports can produce high levels of continuous or intermittent noise, which, upon continued exposure, may have both short- and long-term impacts. Relevant short-term impacts are the experience of annoyance (a general feeling of nuisance caused by noise) and sleep disturbance, which affect wellbeing and impair both physical and mental performance. As for long-term impacts, a growing body of evidence points to a relation between long-term exposure to transportation noise and increasing incidence of cardiovascular and metabolic diseases, effects on cognitive development (in children), and effects on mental health
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Recently, several studies on pedestrian safety and particularly those addressing pedestrian crossing behaviour and decision-making, have been performed using virtual reality systems. The use of simulators to assess pedestrian behaviour is... more
Recently, several studies on pedestrian safety and particularly those addressing pedestrian crossing behaviour and decision-making, have been performed using virtual reality systems. The use of simulators to assess pedestrian behaviour is conditioned by the feeling of presence and immersion, for which the sound is a determining factor. This paper presents an implementation procedure in which tyre-road noise samples are auralized and presented as auditory stimuli in a virtual environment, for assessing pedestrian crossing decision-making. The auditory samples obtained through the Close Proximity (CPX) method and subsequently auralized to represent Controlled Pass-By (CPB) sounds reproduce the sounds of a vehicle approaching a crosswalk. The auralized sounds together with the presentation of visual stimuli composed an experiment which was carried out with 30 participants. Safety indicators, as the time-to-passage at the moment that participants decided to cross a virtual crosswalk and...
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The aim of this research is to develop multifunctions on recycled asphalt mixtures for the surface layer of road pavements. Therefore, preliminary research on functionalization has been carried out. Afterwards, the asphalt mixtures were... more
The aim of this research is to develop multifunctions on recycled asphalt mixtures for the surface layer of road pavements. Therefore, preliminary research on functionalization has been carried out. Afterwards, the asphalt mixtures were designed and characterized by mechanical and superficial point of views. The next step is the design of the nanomaterials, their application on asphalt mixtures and the characterization from physical, mechanical and superficial behavior.
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The alarmingly high recorded accident rate in recent years has received a considerable attention from the road authorities resulting in stronger prevention campaigns. Irrespective of the meritorious efforts of relevant institutions, the... more
The alarmingly high recorded accident rate in recent years has received a considerable attention from the road authorities resulting in stronger prevention campaigns. Irrespective of the meritorious efforts of relevant institutions, the number of victims due to accidents increases yearly. From theoretical training of drivers, the conditions of the roads and the culture of citizens are among some reasons that contribute to this endemic, that affect many families on daily basis. The weather conditions can be unpredictable, placing additional requirements on the vehicle and driver?s skills to handle with the vehicle and the environment. The presence of snow or ice on the road can make driving difficult. Wet snow can make muddy roads and can also build up in the vehicle wheel cavities affecting the driving ability. The horizontal and vertical road marking signs are two simple methods of visual alert for the state of road surface. In this work, we describe the use of a material colour layer sensor, applied on the road surface, which works due to the colour change of horizontal road markings, as a result of temperature change of pavement and ice occurrence. These road pavements as well as intelligent road signs will warn drivers the presence of ice patches, and thus, contributing to minimize the occurrence of accidents.info:eu-repo/semantics/publishedVersio
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Nowadays, there is increasing concern in transportation engineering about the use of techniques less harmful to the environment and also about road safety. Heterogeneous photocatalysis based on the application of semiconductor materials... more
Nowadays, there is increasing concern in transportation engineering about the use of techniques less harmful to the environment and also about road safety. Heterogeneous photocatalysis based on the application of semiconductor materials onto asphalt mixtures is a promising technology because it can mitigate air pollution and road accidents. The functionalized asphalt mixtures with photocatalytic capability can degrade pollutants, such as damaging gases and oil/grease adsorbed on their surface, from specific reactions triggered by sunlight photons, providing significant environmental and social benefits. In this article, a review of photocatalysis applied in asphalt mixtures is presented. The most important characteristics related to the functionalization of asphalt mixtures for photocatalytic applications and their corresponding characterization are presented, and the achieved main results are also discussed.
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Leidy Baron, Jocilene Costa, Maria Alice Prudêncio Jacques, Elisabete Freitas, Susana Faria 1 Universidade do Minho, Departamento de Engenharia Civil, Campus de Azurém, 4800-058, Guimarães, Portugal 2 Universidade Federal de... more
Leidy Baron, Jocilene Costa, Maria Alice Prudêncio Jacques, Elisabete Freitas, Susana Faria 1 Universidade do Minho, Departamento de Engenharia Civil, Campus de Azurém, 4800-058, Guimarães, Portugal 2 Universidade Federal de Pernambuco-UFPE, Centro Acadêmico do Agreste, 55014-900, Caruaru/PE, Brasil 3 Universidade de Brasília, Programa de Pós-Graduação em Transportes, Campus Darcy Ribeiro, 70910-900, Brasília/DF, Brasil
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In this communication the optical characterization of asphalt mixture improved by the incorporation of photocatalytic semiconductors is addressed. Road pavements must have the ability to resist the effects of climate and vehicle traffic... more
In this communication the optical characterization of asphalt mixture improved by the incorporation of photocatalytic semiconductors is addressed. Road pavements must have the ability to resist the effects of climate and vehicle traffic ensuring safety comfort and economy with low environmental impact. The incorporation of photocatalytic into the asphalt gives it an extra ability to reduce the amount of important pollutants in air. The photocatalytic performance is evaluated by optical analysis using spectrophotometry, namely UV/visible diffuse reflectance and absorbance spectroscopies, allowing the calculation of the semiconductors’ band gap and to analyze the photocatalytic activity by a dye degradation. Optical microtopographic inspection of the photocatalytic asphalt mixtures is performed to evaluate skid resistance of the pavements.Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/201
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The determination of the band gap energy of semiconductors is important for the understanding of the production of the electron/hole pairs under the light irradiation, which, in the case of photocatalytic materials, are related to their... more
The determination of the band gap energy of semiconductors is important for the understanding of the production of the electron/hole pairs under the light irradiation, which, in the case of photocatalytic materials, are related to their properties and efficiency. The photoexcited electrons and holes are good reductant and powerful oxidant species, respectively. As consequence the free radicals formed can to degrade, after a sequence of redox reactions, various pollutants present in water or air. Diffuse Reflectance Spectroscopy (DRS) is a technique frequently employed to study the optical properties of solids. In this context, the Kubelka-Munk model (K-M model) [1] has been extensively applied to investigate the light scattered diffusely from the surface of semiconductor materials in the form of powders including composite materials. However, in some papers published recently, including some in prestigious journals in the field of Materials Science, it is possible to perceive some i...
Light and heat are relevant factors for road pavements since they promote the aging of the asphalt surfaces [1], and a large amount of heating can intensify the Urban Heat Island (UHI) effect [2]. Contrariwise, the lack of light strongly... more
Light and heat are relevant factors for road pavements since they promote the aging of the asphalt surfaces [1], and a large amount of heating can intensify the Urban Heat Island (UHI) effect [2]. Contrariwise, the lack of light strongly affects visibility conditions, reducing safety [3]. The conventional black color of asphalt pavements absorbs light and stores a large amount of thermal energy, which can be reduced opting by the application of light-colored pavements using, for example, a transparent binder [3]. Industrial activities and road traffic are the main sources of pollutant emissions, mostly SO2 and NOx, which are hazardous atmospheric pollutants. There are several consequences at different scales caused by these harmful gases, such as intensification of the greenhouse effect, acid rain, and public health problems. With the use of nano-TiO2 into/over asphalt mixtures, and consequently with the functionalization process considering the photocatalytic and self-cleaning prop...
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(PTDC/ECMTRA/3568/2014), financiado por fundos nacionais atraves da FCT e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional atraves do Programa Operacional Competitividade e Internacionalizacao (POCI), e da bolsa de doutoramento... more
(PTDC/ECMTRA/3568/2014), financiado por fundos nacionais atraves da FCT e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional atraves do Programa Operacional Competitividade e Internacionalizacao (POCI), e da bolsa de doutoramento SFRH/BD/131638/2017 financiada pela FCT
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Este trabalho enquadra-se nas atividades do projeto de investigacao AnPeB – Analise do comportamento de peoes com base em ambientes simulados e sua incorporacao na modelacao de risco (PTDC/ECM-TRA/3568/2014), foi financiado no âmbito do... more
Este trabalho enquadra-se nas atividades do projeto de investigacao AnPeB – Analise do comportamento de peoes com base em ambientes simulados e sua incorporacao na modelacao de risco (PTDC/ECM-TRA/3568/2014), foi financiado no âmbito do projeto Promover a Producao Cientifica e Desenvolvimento Tecnologico e a Constituicao de Redes Tematicas (3599-PPCDT) e comparticipado pelo Fundo Comunitario Europeu FEDER. De referir ainda a Fundacao para a Ciencia e a Tecnologia devido ao financiamento da bolsa de doutoramento SFRH/BD/131638/2017.
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This paper identifies and analyzes variables that influence pedestrian safety based on the definition of models of pedestrian crash frequency for urban areas in Portugal. It considers three groups of explanatory variables, namely: (i)... more
This paper identifies and analyzes variables that influence pedestrian safety based on the definition of models of pedestrian crash frequency for urban areas in Portugal. It considers three groups of explanatory variables, namely: (i) built environment; (ii) pedestrian infrastructure, and (iii) road infrastructure, as well as exposure variables combining pedestrian and vehicular traffic volumes. Data on the 16 variables considered were gathered from locations in the counties of Braga and Guimarães. The inclusion of pedestrian infrastructure variables in studies of this type is an innovation that allows for measuring the impacts of the dimensions recommended for this type of infrastructure and assessing the implementation of policies to support the mobility of vulnerable users, especially pedestrians. Examples of such variables are unobstructed space for pedestrian mobility and the recommendable distance separating regulated crossings. Zero-Truncated Negative Binomial Regression Mode...
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This work evaluated the photocatalytic activity of 3D-printed cementitious mortar specimens functionalized with TiO2 nanoparticles to obtain a multifunctional and smart concrete. This research aims to assess the influence of different... more
This work evaluated the photocatalytic activity of 3D-printed cementitious mortar specimens functionalized with TiO2 nanoparticles to obtain a multifunctional and smart concrete. This research aims to assess the influence of different parameters related to the functionalization process such as adsorption, coating time gaps, and coating rates on the degradation efficiency of the functionalized cementitious specimens. Each specimen was evaluated under the degradation of Rhodamine B (RhB) in an aqueous solution using a sun-light simulation. The obtained results showed a decrease in adsorption (under dark condition) with increasing the sample curing age. The highest photocatalytic efficiency was observed for coated samples aged 7 days. By increasing the coating rates, the photocatalytic efficiency is enhanced. Nonetheless, regardless of the coating rates, all the specimens showed an increase in photocatalytic efficiency for longer time periods of light exposition, i.e., after 8 h of irr...
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Transparent binder is used to substitute conventional black asphalt binder and to provide light-colored pavements, whereas nano-TiO2 has the potential to promote photocatalytic and self-cleaning properties. Together, these materials... more
Transparent binder is used to substitute conventional black asphalt binder and to provide light-colored pavements, whereas nano-TiO2 has the potential to promote photocatalytic and self-cleaning properties. Together, these materials provide multifunction effects and benefits when the pavement is submitted to high solar irradiation. This paper analyzes the physicochemical and rheological properties of a transparent binder modified with 0.5%, 3.0%, 6.0%, and 10.0% nano-TiO2 and compares it to the transparent base binder and conventional and polymer modified binders (PMB) without nano-TiO2. Their penetration, softening point, dynamic viscosity, master curve, black diagram, Linear Amplitude Sweep (LAS), Multiple Stress Creep Recovery (MSCR), and Fourier Transform Infrared Spectroscopy (FTIR) were obtained. The transparent binders (base and modified) seem to be workable considering their viscosity, and exhibited values between the conventional binder and PMB with respect to rutting resis...
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When crossing a road, pedestrians must detect traffic, combine data coming from different perceptual modalities, evaluate the time envelope for safely cross the street, and monitor the position of oncoming vehicles to perform corrective... more
When crossing a road, pedestrians must detect traffic, combine data coming from different perceptual modalities, evaluate the time envelope for safely cross the street, and monitor the position of oncoming vehicles to perform corrective actions if needed. This study analyzed the influence of noise emitted by vehicles, or its absence, on pedestrians’ crossing decision-making. Experiments were performed in a virtual environment using two road scenarios. Participants were presented with stimuli of approaching vehicles that varied regarding speed, movement patterns, and auditory condition: one concerning the approaching of an electric vehicle, another regarding the approaching of a gasoline combustion vehicle, and, finally, a condition regarding the absence of auditory cues. Participants were tasked with indicating the moment when they decided to cross the street. The results show that, despite the noise variations caused by the type of vehicle and its speed pattern, the participants’ d...
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A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), to generate a document that supports the development of future research, compiling the various studies focused on... more
A systematic review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), to generate a document that supports the development of future research, compiling the various studies focused on the analysis of the pedestrian-vehicle interaction at unsignalized crosswalks. Firstly, 381 studies were identified by applying the search protocol in the database sources; however, only nine studies were included in this review because most of the studies are not focused on this type of crosswalks or have not considered the micro-simulation perspective. For each study, an analysis of the used methodology for data collection was carried out, in addition to what type of model it was applied, including the variables that represent the PVI (Pedestrian-Vehicle Interaction). The outcomes obtained by this systematic review show that although the video camera observation technique is the most used, it is possible to complement them with other tools to add...
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ABSTRACT This work comprises the study of asphalt mixtures produced with cork and rubber granulates as partial aggregate substitutes. Although these alternative materials are considered waste, they might contribute to reduce tyre–road... more
ABSTRACT This work comprises the study of asphalt mixtures produced with cork and rubber granulates as partial aggregate substitutes. Although these alternative materials are considered waste, they might contribute to reduce tyre–road interaction noise and therefore, to promote pavements’ sustainability. However, their incorporation into asphalt mixtures must not compromise their mechanical performance. Thus, as a first step to the subject, laboratory tests were conducted on two asphalt mixtures containing rubber or cork granulates and their performance was compared to that of a conventional mixture. Promising results were obtained for the alternative mixtures, making them ready for testing their acoustic performance.
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Road pavement develops distresses over time, which increase tyre/road noise. This work focuses on the impact of these distresses on environmental noise. To calculate the environmental noise, a method to transform Close ProXimity (CPX)... more
Road pavement develops distresses over time, which increase tyre/road noise. This work focuses on the impact of these distresses on environmental noise. To calculate the environmental noise, a method to transform Close ProXimity (CPX) measurement results into the required input for traffic noise models was defined and used. The tyre/road noise levels were determined by the CPX method for three types of pavement, with three types of distress, at three different speed levels. The study was carried out in the city center of Guimarães, a medium-sized Portuguese city. Using the NMPB model, 18 noise maps were produced for the passing of one single vehicle, taking into account two levels of distress (50% and 100%) for the pavement. The presence of distresses increased the noise, calculated at control points, by up to 7.1 dBA, and the percentage of the population exposed to levels over 45 dB was more than 11%. It was shown that pavement maintenance at early stages of distress development is...
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The development of a linear mixed model to describe the degradation of friction on flexible road pavements to be included in pavement management systems is the aim of this study. It also aims at showing that, at the network level, factors... more
The development of a linear mixed model to describe the degradation of friction on flexible road pavements to be included in pavement management systems is the aim of this study. It also aims at showing that, at the network level, factors such as temperature, rainfall, hypsometry, type of layer, and geometric alignment features may influence the degradation of friction throughout time. A dataset from six districts of Portugal with 7204 sections was made available by the Ascendi Concession highway network. Linear mixed models with random effects in the intercept were developed for the two-level and three-level datasets involving time, section and district. While the three-level models are region-specific, the two-level models offer the possibility to be adopted to other areas. For both levels, two approaches were made: One integrating into the model only the variables inherent to traffic and climate conditions and the other including also the factors intrinsic to the highway characte...
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ABSTRACT Pavement engineering has been one of the emerging areas in the use of nanomaterials due to the capacity that these nanostructured materials have in modifying surfaces such as asphalt materials by properties such as water and oil... more
ABSTRACT Pavement engineering has been one of the emerging areas in the use of nanomaterials due to the capacity that these nanostructured materials have in modifying surfaces such as asphalt materials by properties such as water and oil repellency, anti ice, among others. The accession of the ice is correlated with the physico-chemical properties of the surface of solid materials such as asphalt. This phenomenon has serious consequences and impacts, particularly in temperate countries, inter alia, with regard to road safety and the mechanical strength of the pavement. In this work, a new asphalt material with antifreeze and super hydrophobic properties was studied and developed using nanostructured materials like surface modifier agent. The surface of asphalt material was nanocoated by wet chemical process and characterized by particle size measures using a Malvern Instruments Nanosizer. The morphological and physico-chemical properties were characterized by XPS, AFM, SEM, EDS and MEVT. The characterization as its hydrophobicity were made contact angle measures using distilled water and ice was logged behavior anti test under controlled environment at a temperature of -10° c. The samples were also subjected to wear test according to EN 10974. The results demonstrated that the asphalt material presented an excellent superhydrophobic behavior, with an angle of 163º and an inhibitor of adherence of ice. After the test of wear the superhydrophobic effect was maintained. This work constitutes a significant advance in the application of antifreeze and superhydrophobic surfaces and an important development for road engineering.
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The standards for the environmental quality required by the European Community are very demanding in what concerns traffic noise. The interaction tire/road is undoubtedly one of the main sources of traffic noise. Nevertheless, standards... more
The standards for the environmental quality required by the European Community are very demanding in what concerns traffic noise. The interaction tire/road is undoubtedly one of the main sources of traffic noise. Nevertheless, standards do not account for the increase in the noise level caused by wet road surfaces. Therefore, the aim of this work is to study the effects of water on pass-by noise since the weather is rainy about 25 per cent of the year in Portugal. Thus, it addresses two currently used pavement surfaces, porous asphalt and dense asphalt, constructed in a motorway. A version of the Statistical Pass-By Method was used to assess noise levels with dry and wet surfaces, using a selected set of heavy and light vehicles. The results include analysis of the statistical pass-by index, maximum noise levels and noise spectrum. Noise levels increase considerably with the presence of water, shifting the overall noise by 4 dB(A). The benefits of porous asphalt are very limited for heavy vehicles, particularly at high speeds.
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Top-down cracking (TDC) is a flexible pavement distress caused by a number of factors, including high contact stresses from truck tires, mix design characteristics, (e.g., binder type and aggregate gradation) and poor construction... more
Top-down cracking (TDC) is a flexible pavement distress caused by a number of factors, including high contact stresses from truck tires, mix design characteristics, (e.g., binder type and aggregate gradation) and poor construction quality, (e.g., segregation and compaction methods). This paper presents the findings of a study seeking to quantify the effect of these factors on TDC. It consists of a laboratory component involving an accelerated Wheel Tracking device and a modeling component involving a 3-D non-linear viscoelastic finite element model. The laboratory component of the study involved 17 asphalt bituminous slabs, constructed to simulate the variation in material properties observed in the field as part of an earlier forensic TDC study. The effect of air voids, bitumen content and type, aggregate gradation and segregation on TDC were studied under 3 temperature conditions. Air voids, segregation and binder content were found to have a significant effect on TDC for all the temperatures tested. Modeling the TDC involved laboratory testing to establish the viscoelastic and tensile strength properties of the asphalt mixtures tested. It was found that the rutted surface contributes significantly to TDC initiation.
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A qualidade ambiental preconizada na legislação europeia, no que respeita ao ruído produzido pelo tráfego rodoviário, é cada vez mais exigente. Por sua vez, a prática portuguesa no domínio da avaliação do ruído rodoviário e o conhecimento... more
A qualidade ambiental preconizada na legislação europeia, no que respeita ao ruído produzido pelo tráfego rodoviário, é cada vez mais exigente. Por sua vez, a prática portuguesa no domínio da avaliação do ruído rodoviário e o conhecimento dos factores que o determinam ainda são insuficientes para satisfazer os requisitos europeus. Assim, neste artigo estuda-se a influência da presença da água no nível de ruído em dois tipos de superfícies usadas correntemente em Portugal. No estudo consideram-se dois trechos consecutivos, integrados na
A41/IC24, uma com camada de desgaste em betão betuminoso drenante e a outra com camada de desgaste em betão betuminoso. A avaliação dos níveis sonoros em cada uma das secções foi realizada pelo Método Estatístico de Passagem. A análise dos resultados integra 3 abordagens, as quais se baseiam no índice estatístico de passagem, no nível de pressão sonora dos veículos de ensaio e no espectro de ruído. Verificou-se que o nível de ruído aumenta significativamente com a presença da água. Esse aumento é determinado pelos níveis de
pressão sonora correspondentes a frequências superiores a 500 Hz, quando se trata de veículos pesados. No caso dos veículos ligeiros esse aumento é mais significativo a frequências
superiores a 1000 Hz, particularmente na camada em betão betuminoso.
A41/IC24, uma com camada de desgaste em betão betuminoso drenante e a outra com camada de desgaste em betão betuminoso. A avaliação dos níveis sonoros em cada uma das secções foi realizada pelo Método Estatístico de Passagem. A análise dos resultados integra 3 abordagens, as quais se baseiam no índice estatístico de passagem, no nível de pressão sonora dos veículos de ensaio e no espectro de ruído. Verificou-se que o nível de ruído aumenta significativamente com a presença da água. Esse aumento é determinado pelos níveis de
pressão sonora correspondentes a frequências superiores a 500 Hz, quando se trata de veículos pesados. No caso dos veículos ligeiros esse aumento é mais significativo a frequências
superiores a 1000 Hz, particularmente na camada em betão betuminoso.
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Este artigo tem por objectivo o estudo da geração do ruído resultante da interacção da superfície de dois tipos de pneus com dois tipos de pavimentos rodoviários, sendo composto por duas partes. Na primeira parte apresenta-se o estado da... more
Este artigo tem por objectivo o estudo da geração do ruído resultante da interacção da superfície de dois tipos de pneus com dois tipos de pavimentos rodoviários, sendo composto
por duas partes. Na primeira parte apresenta-se o estado da arte relativamente à influência das
características dos pneus no ruído e na segunda um caso de estudo. O estudo decorreu em duas secções de pavimento consecutivas, com camadas de desgaste em betão betuminoso
drenante e em betão betuminoso denso. Os ensaios foram realizados pelo Método de ensaio
dos níveis das emissões sonoras de pneu em estrada – Ensaio com motor desligado, tendo sido efectuadas 64 passagens a velocidades compreendidas entre 70 km/h e 90 km/h com dois
veículos equipados com pneus diferentes. Para as condições do estudo, pode concluir-se que a
variação do nível de ruído resultante do tipo de pneu reduz à medida que a velocidade aumenta e que a escultura do pneu influenciou os mecanismos geradores de ruído, provocando uma diferença de 1 dB (A) no nível de ruído.
por duas partes. Na primeira parte apresenta-se o estado da arte relativamente à influência das
características dos pneus no ruído e na segunda um caso de estudo. O estudo decorreu em duas secções de pavimento consecutivas, com camadas de desgaste em betão betuminoso
drenante e em betão betuminoso denso. Os ensaios foram realizados pelo Método de ensaio
dos níveis das emissões sonoras de pneu em estrada – Ensaio com motor desligado, tendo sido efectuadas 64 passagens a velocidades compreendidas entre 70 km/h e 90 km/h com dois
veículos equipados com pneus diferentes. Para as condições do estudo, pode concluir-se que a
variação do nível de ruído resultante do tipo de pneu reduz à medida que a velocidade aumenta e que a escultura do pneu influenciou os mecanismos geradores de ruído, provocando uma diferença de 1 dB (A) no nível de ruído.