Andrea Simone

Laser Scanning on Road Pavements: A New Approach for Characterizing Surface Texture

The surface layer of road pavement has a particular importance in relation to the satisfaction of the primary demands of locomotion, such as security and eco-compatibility. Among those pavement surface characteristics, the “texture” appears to be one of the most interesting with regard to the attainment of skid resistance. Specifications and regulations, providing a wide range of functional indicators, act as guidelines to satisfy the performance requirements. This paper describes an experiment on the use of laser scanner techniques on various types of asphalt for texture characterization. The use of high precision laser scanners, such as the triangulation types, is proposed to expand the analysis of road pavement from the commonly and currently used two-dimensional method to a three-dimensional one, with the aim of extending the range of the most important parameters for these kinds of applications. Laser scanners can be used in an innovative way to obtain information on areal surface layer through a single measurement, with data homogeneity and representativeness. The described experience highlights how the laser scanner is used for both laboratory experiments and tests in situ, with a particular attention paid to factors that could potentially affect the survey.

Discrete particle element analysis of aggregate interaction in granular mixes for asphalt: combined DEM and experimental study

The conventional approach to modeling asphaltic materials is to treat them at macro-scale using continuum-based methods. Numerous research works, however, show that for these mixtures it’s very important to take into account their micromechanical behaviour, at the scale of aggregate particles, because it is a primary factor in terms of overall system performance. In this way the Distinct Particle Element Method (DEM) represents a very useful tool.

Incorporation of Rubber Powder as Filler in a New Dry-Hybrid Technology: Rheological and 3D DEM Mastic Performances Evaluation

In recent years, the use of crumb rubber as modifier or additive within asphalt concretes has allowed obtaining mixtures able to bind high performances to recovery and reuse of discarded tires. To date, the common technologies that permit the reuse of rubber powder are the wet and dry ones. In this paper, a dry-hybrid technology for the production of Stone Mastic Asphalt mixtures is proposed. It allows the use of the rubber powder as filler, replacing part of the limestone one. Fillers are added and mixed with a high workability bitumen, modified with SBS (styrene-butadiene-styrene) polymer and paraffinic wax. The role of rubber powder and limestone filler within the bituminous mastic has been investigated through two different approaches. The first one is a rheological approach, which comprises a macro-scale laboratory analysis and a micro-scale DEM simulation. The second, instead, is a performance approach at high temperatures, which includes Multiple Stress Creep Recovery tests. The obtained results show that the rubber works as filler and it improves rheological characteristics of the polymer modified bitumen. In particular, it increases stiffness and elasticity at high temperatures and it reduces complex modulus at low temperatures.

Semi-automatic Evaluation of the Degree of Bitumen Coverage on Bitumen-Coated Aggregates

EN 12697-11 is the standard providing test methods for evaluating affinity between aggregate and bitumen and its influence on the susceptibility of the mixture to stripping. Among the methods, the rolling bottle test has a number of advantages in terms of rapidity, low costs, and suitability for routine testing. However, since affinity is assessed by visual registration of two independent operators, results may be altered by a large amount being inevitably subjective. The authors suggest a semi-automatic procedure to overcome potential limits and shortcomings of the method and obtain accurate results. Different mixtures were analyzed and compared, using common natural and recycled aggregates and a 70/100 pen bitumen. The procedure was successfully validated with a manual pixel inspection and confusion matrixes were created. The results showed that the procedure lead to a more reliable registration compared to the standard method and it is suitable, with different accuracies, for both light and dark aggregates.

Reflective Tape Applied to Bicycle Frame and Conspicuity Enhancement at Night

Objective: Four studies were conducted to assess bicyclist conspicuity enhancement at night by the application of reflective tape (ECE/ONU 104) to the bicycle rear frame and to pedal cranks. Background: Previous studies have tested the benefits of reflective markings applied to bicyclist clothing. Reflective jackets however need to be available and worn while reflective markings enhance conspicuity without any active behavior by the bicyclist. Method: In the first study, reflective tape was applied to the rear frame. Detection distance was compared in four conditions: control, rear red reflector, high visibility jacket, and reflective tape. In the second study, the same conditions were studied with night street lighting on and off. In the third study, detection and recognition distances were evaluated in rainy conditions. In the fourth study, visibility was assessed with the reflective tape applied to pedal cranks. Results: In the first study, the application of reflective markings resulted in a detection distance of 168.28 m. In the second study, the detection distance with reflective markings was 229.74 m with public street light on and 256.41 m with public street light off. In rainy conditions, detection distance using the reflective markings was 146.47 m. Reflective tape applied to pedal cracks resulted in a detection distance of 168.60 m. Conclusion: Reflective tape applied to the rear bicycle frame can considerably increase bicyclist conspicuity and safety at night. Application: Reflective tape is highly recommended to complement anterior and rear lights in bicycle riding at night.

Modular model building for vehicular traffic systems with macroscopic dynamics

Abstract Vehicular traffic modeling, analysis and supervision has became in the last year very attractive both for engineers and mathematicians with the aim of understanding, controlling and forecasting traffic phenomena. In this framework, the use of simulation tools has spread rapidly both to adequately perform the design of a road infrastructure, and as a support to simulate and verify the road infrastructure. Currently available simulators are in general closed systems where designers have no access to the implemented models, do not permit the integration of macroscopic and microscopic models together and are usually separated from design and verification tools. This paper presents a preliminary study on how to fill these gaps by using a modular model building approach. The developed elementary traffic models have been implemented into Matlab/Simulink environment and collected into a sort of library. The approach has been tested and validated using a real scenario and the available traffic measurements. Copyright ©2011 IFAC.

Fixation distance and fixation duration to vertical road signs

The distance of first-fixation to vertical road signs was assessed in 22 participants while driving a route of 8.34u202fkm. Fixations to road signs were recorded by a mobile eye-movement-tracking device synchronized to GPS and kinematic data. The route included 75 road signs. First-fixation distance and fixation duration distributions were positively skewed. Median distance of first-fixation was 51u202fm. Median fixation duration was 137u202fms with a modal value of 66u202fms. First-fixation distance was linearly related to speed and fixation duration. Road signs were gazed at a much closer distance than their visibility distance. In a second study a staircase procedure was used to test the presentation-time threshold that lead to a 75% accuracy in road sign identification. The threshold was 35u202fms, showing that short fixations to a road signs could lead to a correct identification.

Experimental application of waste glass powder filler in recycled dense-graded asphalt mixtures

This paper presents laboratory study results, including both bituminous mastics and mixtures tests, to assess the use of glass powder (GP) as possible surrogate to limestone filler in recycled dense-graded asphalt mixtures. To achieve a comprehensive approach, the analysis has been divided into three parts including filler, mastics and mixture characterisation. The GP has been completely studied with chemical and physical tests to compare the fundamental characteristics to the commonly used limestone filler. In the second part, rheological tests using the Dynamic Shear Rheometer has been implemented to evaluate fillers interaction with not modified and modified bitumen. Finally, the mechanical properties of the asphalt mixtures containing GP filler were investigated in terms of indirect tensile strength, indirect tensile stiffness modulus and creep characteristics. According to the obtained results, GP filler provided comparable values to limestone filler within both mastic and mixture study. It is noteworthy that from the permanent deformation analysis, both MSCR and RLAT tests confirmed the improvement of rutting resistance with using GP filler.

Light vehicle model for dynamic car simulator

AbstractDriving simulators have been becoming little by little a suitable tool oriented to improve the knowledge about the domain of driving research. The investigations that can be conducted with this type of tool concern the driver’s behaviour, the design/control of vehicles, testing assistance systems for driving and the roadway infrastructure’s impact. The benefits of simulation studies are many: lack of any real risk to users, reproducible situations, time savings and reduced testing costs. In addition, their flexibility allows to test situations that do not exist in reality or at least they rarely and randomly exist. The topic of the present work concerns the development of a brand new dynamic model for an existing car simulator owned by LEPSIS laboratory (Laboratoire d’Expliotation, Perception, Simulateurs et Silulations – Laboratory for Road Operations, Perception, Simulators and Simulations) belonging to COSYS (COmposants et SYStems), which is a department of IFSTTAR institute (Institut Francais ...

Effects on Bonding of Anti-reflective Cracking Solutions at the Top Bituminous Interface of a Small Airport Pavement: A Laboratory and Modeling Study

The maintenance of bituminous airport pavements is of high concern when the limited available time for interventions and the performance effectiveness of the adopted materials are considered. In many cases, due to their former military vocation, small airport pavements have robust, sound and durable foundations that seldom require deep interventions of maintenance. Thus, it is more often needed to rehabilitate the pavement bituminous surface layers to restore the functional characteristics of the runaway and to protect the bottom layers from water leaching through the surface damages (e.g. cracks). This paper shows an example of airport pavement maintenance that was designed to rehabilitate the wearing course of a cracked bituminous structure that was proven to have sufficient bearing capacity. In order to prevent the reflection of cracks on the new layer, the effects of using both a geosynthetic net and a Stress Absorbing Membrane Interlayer (SAMI) were investigated at the old-new materials interface. The effects of debonding and the potential risk of slippage or delamination of the new wearing course were assessed by means of laboratory direct shear tests and multilayer elastic pavement system modeling.