1,721,084 research outputs found
Safety performance functions for road intersections in the Friuli Venezia Giulia region
Full text linkThe aim of this paper was developing Safety Performance Functions (SPFs) of four different types of road intersections: unsignalized three-leg intersection, unsignalized four-leg intersection, signalized threeleg intersections, signalized four-leg intersection. The data on accidents and traffic volume of 28 intersections, which are under the jurisdiction of Friuli Venezia Giulia Strade S.p.A., were collected and analyzed. To model the empirical relation between crash frequency and traffic volume, a feed-forward artificial neural network (ANN), characterized by the hyperbolic tangent transfer function and one hidden layer, was used. SPFs of the analyzed road intersections have shown a slope reduction of the tangent line when annual average daily traffic increased on the main leg, namely, the road capacity is not able to meet the increase in the volume of traffic. As a result, this leads to a saturation that induces slowdowns with a lower probability of running into an accident
Fuzzy logic for cross-layer optimization in cognitive radio networks[cognitive radio communications and networks]
No full textThe search for the ultimate architecture for crosslayer
optimization in cognitive radio networks is characterized
by challenges such as modularity, scalability, complexity and
interpretability constraints. In this paper we propose Fuzzy Logic
as an effective means of meeting these challenges, as far as
both knowledge representation and control implementation are
concerned
Creep response of asphalt concretes: Visco-elasto-plasto modeling
No full textThe paper presents and discusses the calibration and validation of a three-dimensional constitutive visco-elasto-plastic model developed for the analysis of the mechanical response of asphalt concretes. The methodology, an inverse problem technique, uses a one-dimensional analytic formulation of the constitutive model and a non-linear constrained optimization based on the Conjugate Gradient algorithm. On the basis of the creep recovery data obtained from an experimental investigation in support of the model calibration, it has been verified that the values of the constitutive parameters can be reliably identified. A subsequent comparison between the experimental creep and numerical curves of the 3-D model demonstrated reasonable shifts, confirming the reliability of the identification procedure for the parameters
Recycling of tyre rubber in porous asphalt using the dry process: a laboratory characterisation
No full textRecycling of tyire rubber in the road pavement, may be one of the best way to reduce waste tires in large quantities and, at the same time, improve some engineering properties of asphalt mixtures.
The paper discusses the results of an experimental study, in order to analyse the potentialities of crumb rubber from road tyres in bituminous mixtures, using the dry process. Two types of porous asphalt mixtures, over the control mixtures without rubber, were formulated by means of the traditional Marshall methodology, and mechanically evaluated by means of the Indirect Tensile Stiffness Modulus test (ITSM), the Creep test (with confinement), and the Indirect Tensile Fatigue Test (ITFT).
Results of this study indicate that the tyre rubber could have a different influence on the performance characteristics, depending on the grading and volumetric properties of the mix being studied: an interesting increase of the fatigue life, a better stiffness behaviour at lower temperatures and a bigger permanent deformation resistance resistance at high temperatures
The use of Construction and Demolition aggregate in unbound sub-base and bituminous bound road base
No full textThis paper presents the results of an investigation, conducted at the University of Padova Road Research Laboratory, to verify the suitability of aggregates from construction and demolition work (C&D: bricks, concretes, etc.) in the formulation of unbound mixes for sub-bases, and bituminous mixes for base layers of road and airport pavements.
The unbound mix samples were prepared using both the Proctor methodology and a gyratory compactor, usually used for the mix-design of bituminous concretes, in order to verify the suitability of the unbound materials. The gyratory press was also used for the formulation of the bituminous mixes, together with the classical Marshall methodology. In both cases, sample compaction with the gyratory technique provided useful information on the shear strength of the mixes and density trend of the material during compaction
Potenziamento strutturale di pavimentazioni stradali ed aeroportuali mediante reti in acciaio composite
No full textLa memoria illustra i più salienti risultati di uno studio teorico ed applicativo relativo al potenziamento strutturale di pavimentazioni stradali ed aeroportuali mediante reti in acciaio, anche in soluzioni composite costituite dall’abbinamento con specifiche miscele bituminose.
Sono state oggetto di analisi ed indagine due applicazioni peculiari: il rinforzo di fondazioni stradali ed aeroportuali mediante rete in acciaio; l’utilizzo di reti abbinate a slurry seal nella manutenzione di sovrastrutture rigide, semirigide e flessibili
Re-use of marginal aggregates in cement bound mixtures for pavement foundations
No full textThe paper reports the results of an experimental study aimed at designing cement bound granular mixtures for pavement foundations, made exclusively with marginal materials, namely electric arc furnace steel slags, ladle furnace slags, waste foundry sands, glass wastes and coal ashes, used with different proportions.
The laboratory investigation has been divided in a preliminary study of physical-geotechnical properties of the by-products, and in the following mechanical characterization of the cement bound mixtures. The formulation of the mixes has been developed in terms of Proctor, compression and indirect tensile strength tests. At the end of the study, the elastic modulus of the mixtures has been determined by means of ultrasonic tests, at different curing periods.
The satisfactory results (compression and indirect tensile strength at 7 days up to 7.33 MPa and 0.74 MPa respectively, depending on the mixtures type), have met the main Italian Contract Specifications, so demonstrating the possibility of using industrial by-products as integral substitutes of the natural aggregates in the production of cement bound granular materials for pavement foundations
FATIGUE BEHAVIOUR AND STIFFNESS PROPERTIES OF ASPHALT RUBBER MIXTURES MADE WITH STEEL SLAGS
No full textThis paper describes the results of a research studying the fatigue resistance performances of bituminous concretes for base courses and wearing courses (traditional and SMA type), made with steel slags and bitumen modified with crumb rubber or SBS polymers. The fatigue behaviour was also investigated in conditions of long-term ageing, in order to evaluate the effectiveness of the modification with crumb rubber using the wet process in reducing the fatigue damage in heavily oxidized mixtures. The experimental data, obtained from four point bending tests (4PBT), were interpreted both with the classical methodology based on a 50% reduction of the initial stiffness and with Pronk’s energy approac
PERMANENT DEFORMATION RESISTANCE OF ASPHALT CONCRETES MADE WITH ELECTRIC ARC FURNACE STEEL SLAGS
No full textFor some time now, under the pressure of a growing public awareness of the environmental problems linked with the disposal of industrial by-products, the scientific community has dedicated an increasing attention to the subject of the recovery and recycling of “marginal aggregates”, as for instance, steel slags.
The paper describes the permanent deformation evaluation of both conventional and high performance asphalt concretes (Stone Mastic Asphalt, wearing course and base course asphalt concretes), for motorway pavements, made with Electric Arc Furnace (EAF) steel slags in substitution of the natural aggregates.
The experimental investigation, carried out at the Road Research Laboratory of the University of Padua, involved a chemical, physical, and mechanical characterization of the EAF steel slags, followed by the mix design and the permanent deformation evaluation of the asphalt concretes, by means of Repeated Load Axial Tests (RLAT) and Wheel Tracking Tests (WTT).
The requisites for acceptance in the main Italian Contract Specifications were completely satisfied (Indirect Tensile Strength up to 1.42 MPa, depending on the mixture) and the mechanical performance, in terms of permanent deformation resistance, resulted really interesting and promising. Therefore it has been experimentally verified that the EAF steel slags can be successfully recycled in the stone skeleton of the asphalt concretes investigated, moreover with extremely high content (from 89% to 93% by weight)
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