133 research outputs found
Contribuição da superfície dos pavimentos para a produção de ruído
O ruído rodoviário constitui actualmente um problema grave de qualidade ambiental,
que resulta essencialmente dos mecanismos de contacto entre o pneu e a superfície do
pavimento. Por conseguinte, a avaliação em termos acústicos das superfícies da rede
rodoviária é importante. Assim, neste artigo estuda-se a contribuição de um conjunto de 7
superfícies de pavimentos em serviço para a produção de ruído rodoviário: 1 em betão
betuminoso denso; 1 em betão betuminoso rugoso, 2 em microbetão betuminoso rugoso; 1 em
betuminoso rugoso com betume modificado com borracha e 2 misturas abertas com betume
modificado com borracha. A metodologia de ensaio baseou-se no Método Estatístico de
Passagem. Para o estudo foram seleccionados 2 veículos ligeiros e um pesado de 2 eixos, os
quais fizeram um total de 188 passagens a 3 níveis de velocidade. A cada passagem registouse
o nível de ruído máximo, a velocidade efectiva dos veículos, a velocidade do vento e a
temperatura do ar e da superfície do pavimento. Desta avaliação resulta que, relativamente ao
betão betuminoso denso, as superfícies mais silenciosas são as de microbetão betuminoso
rugoso e de mistura aberta com betume modificado com borracha, apresentando reduções
entre os 4 e os 8 dB(A).Auto-estradas do Norte, S.A (AENOR)Estradas de Portugal (E.P.) Direcção de Braga
Contribution of asphalt rubber mixtures to noise abatement – time effect
Wearing course layers with a rubberized asphalt binder have been lately recommended as a
measure to mitigate noise. Their acoustical performance in an early age seems to be
superior to that shown by conventional layers. Nevertheless, there is no deep knowledge in
relation to their behavior throughout their lifetime. The research carried out aims at observing
and studying this type of mixes. For this purpose, several road sections with gap-graded
mixtures, two of which with rubberized asphalt, were selected. On each road section the tyreroad
noise generated by two light vehicles was measured by means of pass-by tests. After
three years, those tests were repeated under the same conditions. The results focused on
the comparison of the noise level versus speed among layers at the same testing time and
on the same layers with different ages. The results obtained three years ago showed that
gap-graded asphalt rubber mixtures have a similar performance than that of other type of
gap-graded thin mixtures. The same performance was observed in the recent tests. On
average, an increase of 4.0 to 4.5 dB(A) was determined for the two surfaces with rubberized
asphalt, which had the same increase on noise as the control surface.(undefined
Desempenho de barreiras acústicas : dois métodos de avaliação
Em Portugal tem-se verificado um crescimento exponencial da colocação de barreiras acústicas, como meio de resposta às exigências de qualidade ambiental definidas pela Comunidade Europeia. Este facto tem como consequência a necessidade de verificação do desempenho destes dispositivos, particularmente do isolamento sonoro aéreo. Assim, no presente artigo apresentam-se as orientações da Norma Europeia CEN/TS 1793-5:2003, relativa ao método de ensaio para determinar o isolamento sonoro aéreo dos dispositivos de redução do ruído, e uma metodologia expedita, que poderá ser usada como indicativa do desempenho destes dispositivos. Para as duas metodologias apresenta-se o princípio e procedimento de ensaio, o equipamento e a forma de avaliação do desempenho. Apresenta-se ainda a avaliação do desempenho de 3 barreiras acústicas, constituídas por materiais diferentes, feita através do método expedito. Finalmente, são feitas algumas considerações quanto aos métodos apresentados, prevendo-se que a metodologia preconizada na norma europeia seja de difícil execução in situ, especialmente em zonas de relevo acidentado. A avaliação do desempenho das barreiras acústicas com o recurso a estas metodologias, em diferentes fases do seu ciclo de vida, poderá constituir uma solução vantajosa e fiável
Noise absorption of gap graded mixtures with rubberized asphalt
Sound absorption is a material property which contributes to reduce noise levels when sound
propagates from the source to the receiver. Porous materials have particularly good
absorption characteristics, not only because of the high percentage of air voids, but also due
to their flow resistance and tortuosity. Road surface layers made of gap graded mixtures are
among those absorptive materials. Because these mixtures have a void content that may be
considered of medium level, this study aims to characterise their absorption capacity,
particularly of those with rubberized asphalt binder. For this purpose, absorption
measurements in a Kundt’s tube were performed on cores extracted from slabs with different
gap graded asphalt. In order to study the effect of the rubberized asphalt, the mixtures were
produced in laboratory with two types of rubberized asphalt and with unmodified asphalt. The
effect of the binder was pondered with this procedure. Furthermore, the effect of porosity was
considered bycomparing the results of mixtures which have considerably high and low void
contents.(undefined
Assessment of the traffic noise on thin layers
Traffic noise is an important branch of the environment pollution which deeply affects
the population and for that reason it has been included in the set of pavement
performance indicators. Nevertheless, the knowledge on the environmental impact of
the existing surface pavement layers is very limited, particularly for what respects to
tyre/road noise of thin layers. These layers are at the present time widely used in a great
extent with rubberized asphalt both in urban and rural roads especially in the north of
Portugal due to environmental concerns. In this paper the comparison of the tyre/road
noise (Lmax) generated in roads with thin surface layers is made. The noise levels
generated by light and heavy vehicles are set according to the Statistical Pass-By
Method (SPB) of which test methods is described in the standard ISO 11819-1:1997. At
management level the information provided by tyre/road noise tests is essential to
support environmentally sustainable construction and maintenance alternatives.
Furthermore, at project level, the results give some insight about the relation surface
layers/traffic composition
Análise da qualidade funcional e do impacto ambiental de uma estrada urbana
Este artigo tem por objectivos descrever os principais indicadores da qualidade funcional e
da qualidade ambiental utilizados correntemente a nível da rede e apresentar um caso de
estudo de uma estrada integrada em meio urbano reabilitada recentemente. Esta estrada
contempla três camadas de desgaste diferentes, duas das quais com textura optimizada, com
o objectivo de se estudar o seu efeito no ruído de contacto pneu/pavimento.
Para a observação dos parâmetros técnicos de qualidade funcional (irregularidade, textura e
resistência à derrapagem) foi utilizado um veículo do tipo multifunções e para a medição do
ruído foram efectuadas medições junto à berma com a passagem de veículos a diversas
velocidades.
Com base nesses parâmetros, por um lado, prevê-se que a curto prazo seja necessário
desenvolver-se actividades de conservação da qualidade funcional do pavimento. Por outro
lado, verificou-se que as camadas de desgaste optimizadas reduzem consideravelmente o
impacto do ruído de tráfego no ambiente
Contribution of alternative road surfaces to noise abatement
The increase of noise due to traffic particularly in urban areas has led road administrations to look for low noise surfaces in order to reduce noise impact and to improve environmental quality. This paper aims at assessing the effect of alternative road surfaces on noise abatement. It presents the main results obtained with two distinct experiments, originally intended for other purposes, which address a significant number of non conventional road surfaces. These experiments included nine road surfaces: three of them were gap graded, three contained rubberized asphalt, one had porous asphalt and two had dense asphalt. On these road sections the tyre-road noise generated by two-axle heavy trucks and three-axle heavy trucks and several light vehicles at three levels of speed were measured by means of pass-by tests. Surface texture tests were also performed. The results focused on: i) noise level variation versus speed; ii) estimated noise level for each speed level versus type of surface; iii) the variation of estimated noise level with regards to a reference surface. The best performances were achieved by gap graded mixtures with and without rubberized binder and small grain sizes. The fair behaviour shown by the porous asphalt indicates that the surface texture determined by the grain size seems to influence the noise level more than porosity. Further research on tyre-surface noise should include wide ranges of testing speeds for heavy vehicles, tests with the surface wet, tests that can provide texture spectrum and sound absorption tests
Analysis of the functional quality of pavements from texture measurements
The surface texture of a pavement, including uneveness, is largely determinant of drivers’safety and comfort. It is undoubtedly a major cause of road traffic accidents all over the world. Statistics show that one million killed and 50 million
injured are reported every year by Competent Authorities.
The effect of traffic noise has also become a critical public issue. On the road networking the surface characteristics of pavements also contributed to nearly 80-90% of roadway traffic noise. Not only engines or exhaust systems generate noise.
The impact of tire-surface at speeds above 50 km/h also needs to be added to prime offenders. Functional requirements such as roadway safety, environmental quality, driving comfort and operating costs in the road network are assessed by indicators whose limits are continuously adjusted. The roadway texture is again a main
intervenient.
This paper aims at describing the texture indicators that can be used for the assessment of the texture of a pavement from a network point of view, based on profiles acquired at high speeds, including megatexture.
First an overview of the concepts related to texture and the effects of texture, including unevenness, on safety, driving comfort, ride quality and environmental quality is given. Then, a case study related to a highly trafficked road in the north
of Portugal is presented. This study is the second phase of a broader study that started with the analysis of the structural capacity of that road. In this second phase, a high speed profilometer was used to measure the pavement profile with a
sampling rate which is considered to be adequate for the analysis of longitudinal profile, macrotexture and unevenness. Indicators such as the mean profile depth, the IRI and the rutting depth and the corresponding effects were addressed
Definição e características de superfícies de baixo ruído
As superfícies de pavimentos de baixo ruído são atualmente a medida de redução do ruído preferida pela maioria dos decisores por ser uma medida relativamente barata e por estarem na génese do ruído rodoviário. No entanto, para se averiguar se uma determinada superfície pode ser classificada de “baixo ruído” é fundamental a adoção de um sistema de classificação. Os principais objetivos deste trabalho são apresentar o problema da classificação de pavimentos, discutir a seleção de um limite ou de uma superfície de referência para apoiar a seleção de superfícies com desempenho acústico melhorado e identificar as características que conduzem a níveis de ruído de contato pneu-pavimento mais baixos, abordando-se particularmente a contribuição da macro e da megatextura.FEDE
Contribution of portuguese pavement surfaces to traffic noise
This paper aims at assessing the relative effect of Portuguese pavement surfaces on traffic noise.
It presents the main results obtained with two distinct experiments, originally intended for other
purposes, which address a significant number of thin layers and porous layers.
These experiments included nine road surfaces: three of them were gap graded, three contained
rubberized asphalt, one had porous asphalt and two had dense asphalt. On these road sections the
tyre-road noise generated by two-axle heavy trucks and three-axle heavy trucks and several light
vehicles at three levels of speed were measured by means of pass-by tests. Surface texture tests
were also performed.
The results focused on noise level variation versus speed and estimated noise level for each
speed level versus type of surface. The best performances were achieved by gap graded mixtures
with and without rubberized binder and small grain sizes. The fair behaviour shown by the
porous asphalt indicates that the surface texture determined by the grain size seems to influence
the noise level more than porosity
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