The Use of Bloss Curve in The Exit Lanes of Road Intersections

The paper proposes the use of the Bloss curve (also known as biparametric or bi-hyperclothoid) as a braking curve in the exit lanes of road intersections. The main international standards continue using the clohoid as the principal transitional geometric element, even though the limits of its use in driving regimes with non-uniform speeds are known. The proposal to use the Bloss curve is aimed at overcoming these limitations and opening a debate on the possible need to codify, even in the international standards, the use of more suitable alternative braking curves. In this context, a kinematic study was conducted by comparing the main parameters of the motion (lateral jerk, lateral acceleration, steering speed) between the Bloss curve and more traditional curves, such as clothoid and Generalized Cornu Spirals (GCS). Nine case studies were conducted, each case was characterized considering the type of transition curve used (clothoid, GCS and Bloss curve) and radius R of the exit curve (R = 60 m, 80 m, 100 m). The numerical values assumed by the kinematic variables along the transition curves were "locally" calculated, i.e. "pointby- point", to take into account the non-uniform motion regime. The results obtained, limited to the cases studied, show that the Bloss curve better meets the kinematic conditions of the vehicle motion in non-uniform driving regimes. Therefore, the Bloss curve can be considered as a braking curve in the design of road intersections and be a candidate for further investigation to assess any additional benefits in terms of comfort, driving safety and visual perception of the geometric element

Parametrical analysis of the railways dynamic response at high speed moving loads

The paper introduces some findings about a sensitivity analysis conducted on every geometrical and mechanical parameters which characterize the use of a railway superstructure at the high velocity. This analysis was carried out by implementing a forecast model that is derived from the simplified Gazetas and Dobry one. This model turns out to be particularly appropriate in the explication of problems connected to high velocity, since it evaluates both inertial and viscous effects activated by the moving load speed. The model implementation requires the transfer function determination that represents the action occurred by the bed surfaces on the railway and it therefore contains information concerning the geometrical and the mechanical characteristics of the embankment, of the ballast and of the sub-ballast. The transfer function H has been evaluated with the finite elements method and particularly, by resorting the ANSYS® code with a harmonic structural analysis in the frequencies field. The authors, from the critic examination of the system's dynamics response in its entirety, glean a series of observations both of a general and a specific character, finally attaining a propose of a design modification of the standard railway superstructure at the high velocity of train operation adopted today especially in Italy

Correction to: The vibrations induced by surface irregularities in road pavements – a Matlab® approach

fter publication of this article [1], it is noticed the article contained an error with eq. 12, the c s should be squared. The correct eq. 12 is provided below Document type: Articl

Pavimentazioni stradali provvisorie a servizio dell’utenza

Le pavimentazioni stradali provvisorie usualmente impiegate a servizio dei cantieri stradali sono caratterizzate da notevoli volumi di traffico, generalmente limitati nel tempo, e tendenzialmente da richieste prestazionali contenute. La provvisorietà delle funzioni svolte non si traduce però in una minore complessità delle problematiche da affrontare a livello di progettazione, anzi, per alcuni aspetti queste hanno specifici caratteri di peculiarità da tenere in debita considerazione. Escludendo il caso dei cantieri di breve durata (durata compresa entro 48 ore), la presente memoria pone l’accento sulle tipologie e le fasi costruttive delle infrastrutture provvisorie, sia in ambito urbano che extraurbano, la cui durata in esercizio può protrarsi anche per lungo tempo. Tali infrastrutture devono garantire il transito dei volumi di traffico, e dei carichi propri delle strade interessate dai cantieri, in piena sicurezza ovvero in condizioni di massima efficienza strutturale e funzionale. Pertanto verranno esaminate le diverse tipologie e fasi costruttive delle sovrastrutture provvisorie, in relazione agli ambiti territoriali di pertinenza e alla natura dei cantieri stradali, fermo restando il concetto che “pavimentazione provvisoria” non deve essere sinonimo di “sovrastruttura precaria di fortuna”. Difatti, la presenza di cantieri stradali costituisce di per sé un fattore di rischio per l’utenza che non deve essere incrementato dall’inefficienza della pavimentazione provvisoria. La ricerca della massima sicurezza va perseguita anche a fronte di un impegno finanziario non del tutto trascurabile, in quanto tipologie costruttive flessibili, rigide, etc. sia pur dimensionate con proiezioni di vita utile molto limitata nel tempo, comportano significativi impegni finanziari

Planning of the maintenance of urban roads

The management of urban road pavements is a complex activity which is particularly severe from the economical point of view. In order to optimise the maintenance operations, it is necessary that all the operative phases are co-ordinated within a unique planning system, and therefore the data collected on the pavements conditions are to be used as input for the analysis and the decisions, in order to assess “where”, “when” and “how” to intervene. The paper, starting from the real case of the planning of the maintenance of the urban roads network of the city of Potenza, shows the phases of parameters collection on the fails of the pavements, of data implementing and of interventions planning, defining at the same time a methodology which could be an aid for the planning of the maintenance of the urban roads. The Author proposes the use of the G.E.I. (Global Efficiency Index) of the pavement as an instrument to monitor the evolution with time of the efficiency of the structural pavements from the point of view of global performances. The definition of the G.E.I. function, by means of the assessment of few indicators (e.g. superficial degradation and/or adherence), allows to follow the decay of the pavement itself with time, the G.E.I. decay curve concept being as a consequence defined. This instrument can be placed at disposal of the Administrations of infrastructures and allow to plan the road maintenance for a long period

Sull’applicabilità di un modello diffusivo per la previsione delle concentrazioni di inquinanti da traffico veicolare in ambito urbano

Il fenomeno dell’inquinamento atmosferico da traffico veicolare desta particolari preoccupazioni soprattutto nelle aree urbane, dove elevata è la produzione di inquinanti e dove maggiore è la popolazione esposta al rischio di danni alla salute. La legislazione in materia ha come principale obiettivo la tutela della salute dei cittadini attraverso il controllo della qualità dell’aria, attuato di norma con l’implementazione di opportune reti di monitoraggio capaci di fornire le concentrazioni delle sostanze inquinanti e i parametri metereologici che maggiormente li influenzano. In tale ottica, di estremo interesse è la possibilità di integrare le misurazione oggettive con dati di previsione derivanti dall’applicazione di modelli matematici, opportunamente tarati e calibrati in base alle specificità morfologiche del sito e alle peculiarità del traffico. Nel presente lavoro gli Autori propongono la verifica dell’applicabilità di un modello diffusivo in un’area urbana della città di Potenza, attraverso l’analisi ed il confronto dei livelli di concentrazione previsti con quelli reali registrati da una centralina di monitoraggio. In particolare si è impiegato un modello sperimentale per prevedere la concentrazione di monossido di carbonio in un area attigua all’arteria stradale principale della città di Potenza, caratterizzata da intensi flussi veicolari. I risultati ottenuti, confermando la bontà del modello adottato, consentono di sottolineare come l’ausilio delle previsioni analitiche sia di grande importanza al fine di gestire il fenomeno dell’inquinamento da traffico veicolare, soprattutto in ambito urbano dove tale problema è sentito maggiormente

Mountain Roads’ Geometric Design: Methodological Proposal for Hairpin Bend Design/Retrofitting

Mountainous roads often have to overcome considerable differences in height, which is why hairpin bends find a valid and common use. Despite this, there is a lack of specific international standards. Given the absence of a national standard governing the mountain roads’ design, in Italy, as in many other countries, the Swiss standard SNV 640198a is generally applied. This standard does not guarantee the correct geometric design of hairpin bends for Italian vehicle fleets and fleets according to the Directive 2002/7/EC. In this paper, the authors have developed a new methodology based on the Swiss standard upgrade, which is applicable internationally. Starting from hairpin bends’ geometric layouts provided by SNV 640198a and from related considerations, respectively, to the gyration formulae use and to swept path analysis’ simulations, they developed new planimetric layouts compatible with the vehicle fleet and with the cross-sectional dimensions of Italian roads. In this way, a generally valid methodology applicable to any international context was defined. In particular, the study allowed the definition of new geometric layouts to be used in hairpin bend design/retrofitting when it is necessary to guarantee the simultaneous entry into the bend of a 12 m long bus, and a car travelling in the opposite direction. Finally, the proposed methodology was applied to a mountain road case study in the Lucanian Dolomites area; an area of great tourist, cultural and environmental interest in southern Italy

Indagine reologica e confronto prestazionale di leganti bituminosi modificati da impiegare in ambito stradale

Tra i fattori che maggiormente incidono sulle performances di una pavimentazione di tipo flessibile sono da considerare le proprietà del legante bituminoso impiegato negli strati di superficie. Un approccio razionale finalizzato alla definizione dei parametri reologici del legante consente il superamento delle incertezze connesse ai tradizionali metodi di caratterizzazione dei bitumi. In tal senso, alla luce delle recenti proposte normative definite nell’ambito del progetto S.H.R.P. (Strategic Highway Research Program), il presente lavoro propone il confronto tra le prestazioni reologiche di diversi bitumi, tal quali e modificati, tramite l’impiego di reometro rotazionale (D.S.R. – Dynamic Shear Reomether) e reometro a travetto inflesso (B.B.R. – Bending Beem Rheometer), in dotazione presso il Laboratorio di Costruzioni Stradali dell’Università della Basilicata. In particolare si sono presi in esame due bitumi di penetrazione rispettivamente 80/100 e 50/70, modificati in successione con il polimero SBS a struttura lineare e radiale nelle percentuali pari a 2.5, 5.0 e 7.5%. Si è indagato alle basse temperature (-15, -20 e –25°C) con l’ausilio del B.B.R. effettuando le determinazioni del Modulo di Rigidezza, del Fattore di Rilassamento e delle Temperature LST (Limiting Stiffness Temperature) e LmT (Limiting m-value Temperature). Alle medio-alte temperature (45 e 60°C) la risposta dei leganti è stata determinata impiegando il D.S.R., ricorrendo alle prove di Stress Sweeps, Frequency Sweeps, Time Sweeps, Temperature Sweeps e Multiwaves. Esaminando inoltre i Black Diagrams e i Cole-Cole Diagrams si sono determinate le risposte reologiche dei diversi leganti, definendo quelli a prestazione superiore da impiegare nel confezionamento di conglomerati bituminosi per pavimentazioni stradali

Superpave® mix design method of recycled asphalt concrete applied in the european standards context.

The recycling of road and airport asphalt pavements requires greater reliability of mix design in order to ensure proper rehabilitation and effective reuse of recycled asphalt concrete. Currently, internationally, the most effective mix design procedures for recycled asphalt concrete with RAP (Reclaimed Asphalt Pavement) refer to guidelines developed by SuPerPave® Mixtures Expert Task Group. In this paper, according to the requirements of the European standard EN 13108, the authors investigated the reliability of the above mix design procedure. In particular, the SuPerPave® mix design guidelines were applied for dosing components of wearing course layer recycled asphalt mixture and for the determination of PG (Performance Grade) and critical temperatures of binder contained in RAP (RAP binder) and of binder added ex-novo (virgin binder). The experimental research program started from RAM (Reclaimed Aggregate Material) grading characterization and RAP binder content determination. Afterwards, rheological characterization of the RAP binder and selected virgin binder was carried out using the DSR (Dynamic Shear Rheometer) and BBR (Bending Beam Rheometer) devices. This step allowed us to identify the right virgin binder percentages to be added to RAP binder. Then, in compliance with European standards, the mix design study of recycled mixtures was carried out, identifying the necessary granulometric integrations and the virgin-binder-appropriate percentages to be added. In this phase, three different RAP percentages were used: 30%, 40%, and 50%. Finally, the experimental plan was completed with a preliminary mechanical characterization of the studied recycled asphalt mixtures. The results showed that the implemented rational mix design guarantees performance levels of wearing course layer recycled mixtures that are fully in compliance with European standards