1,721,040 research outputs found
Review of Research on Tire–Pavement Contact Behavior
Full text linkThis article presents the latest progress in research on tire–pavement contact behavior. Firstly, the tire–pavement contact characteristics and their influencing factors are summarized. Then, the measurement methods and theoretical research on tire–pavement contact behavior are reviewed, and the advantages and shortcomings of different methods are compared and analyzed. Finally, analysis in the field of pavement engineering is summarized based on contact behavior. This article suggests a few key research directions: Tire–pavement contact behavior is influenced by multiple factors; therefore, multi-physical field-coupling analyses need to be carried out. Tire–pavement contact tests are mostly static and non-standardized, and it is a future trend to develop high-precision, low-cost, and standardized instruments that can measure dynamic contact. Theoretical research models rarely involve environmental factors; a contact model of the tire, pavement, and environment needs to be constructed that can truly describe the contact process. There is a relationship between contact characteristics and pavement performance; pavement performance evaluation indexes need to be established based on tire–pavement contact characteristics in the future
Indagine sugli Aggregati da C&D
No full textLe Strade presenta, a firma di un team di ricercatori delle Università di Bologna e Pisa, la sintesi di una sperimentazione condotta su un rilevato realizzato ad hoc e finalizzata allo studio di diverse miscele provenienti da costruzioni e demolizioni. L'obiettivo: valutare la capacità portante in prospettiva di un reimpiego in sottofondi e fondazioni stradali. L'indagine ha dimostrato,anche attraverso l'integrazione di compattazione intelligente e prove deflettometriche, che i materiali derivanti da un processo mirato di riciclaggio possono fornire risultati paragonabili, se non superiori, a quelli ottenibili da aggregati vergini
Comparing Light Weight Deflectometer to Standardize their Use in the Compaction Control
No full textThe evaluation of the in situ bearing capacity is evolving from traditional load
plate test (LPT) to dynamic plate testing with deflectometric equipments
(LWD). The rapidity and simplicity of tests implementation allow to reach
levels of hourly productivity up to 30 stations per hour, which correspond to a
considerable reducing of distance between points or to an extension of the
investigated area. The various LWD equipments on the market, conceptually
similar, may record different results. In this study a comparison between two
types of LWD, together with tests to validate two procedures for the assessment
of the compaction level, were undertaken. The comparison was made using data
acquired from several trial sites, with varying materials, thicknesses and levels
of compaction. It was found that the differences between the instruments and
their testing procedures produce results not always congruent. The use of these
deflectometric devices for Qc/Qa calls for the development of instrumentrelated
test procedures, taking into account the variability of site conditions
Exploring Virtual Environments to Assess the Quality of Public Spaces
Full text linkHuman impression plays a crucial role in effectively designing infrastructures that support active mobility such as walking and cycling. By involving users early in the design process, valuable insights can be gathered before physical environments are constructed. This proactive approach enhances the attractiveness and safety of designed spaces for users. This study conducts an experiment comparing real street observations with immersive virtual reality (VR) visits to evaluate user perceptions and assess the quality of public spaces. For this experiment, a high-resolution 3D city model of a large-scale neighborhood was created, utilizing Building Information Modeling (BIM) and Geographic Information System (GIS) data. The model incorporated dynamic elements representing various urban environments: a public area with a tramway station, a commercial street with a road, and a residential playground with green spaces. Participants were presented with identical views of existing urban scenes, both in reality and through reconstructed 3D scenes using a Head-Mounted Display (HMD). They were asked questions related to the quality of the streetscape, its walkability, and cyclability. From the questionnaire, algorithms for assessing public spaces were computed, namely Sustainable Mobility Indicators (SUMI) and Pedestrian Level of Service (PLOS). The study quantifies the relevance of these indicators in a VR setup and correlates them with critical factors influencing the experience of using and spending time on a street. This research contributes to understanding the suitability of these algorithms in a VR environment for predicting the quality of future spaces before occupancy
A laboratory and field recovery estimation of cleaned road surfaces after accidents spills contamination and traffic simulation
No full textContaminant spills from road accidents pose significant challenges to pavement performance and road safety, as they can lead to dangerous driving conditions. This study investigates the impact of vehicle tire passage on cleaned asphalt concrete pavements following hazardous liquid spills. A field trial was conducted to assess the functional characteristics of both cleaned and contaminated surfaces. Laboratory simulations utilising an experimental application of Hamburg Wheel Tracking Device and British Pendulum Tester evaluated pavement deterioration in terms of rutting and skid resistance. The results indicate that hydrocarbon contamination, particularly from petrol and diesel, significantly reduce skid resistance, with engine oil leading to the most substantial decline in performance. Although cleaning procedures can restore some degree of skid resistance, the presence of residual contaminants beneath the surface raises concerns regarding long-term pavement integrity. The variability in skid resistance values among different contaminant types suggests that not all pollutants impact pavement performance equally
The evaluation of the effects of hazardous spills by road accidents on the surface performance of an asphalt-wearing course
No full textAccidental spills of hazardous substances are an important road safety topic due to the reduction of surface performance and the possible structural damage to the pavement. Thus, it is even more important to investigate the consequences of hazardous spills on the functional characteristics of road surfaces and the effects of efficient clean-up operations over time. In the present paper, trial field, laboratory tests and cored samples contaminated with five liquids were carried out on a road pavement to assess the influence of different substances on asphalt features. British Pendulum Tester and micro Grip Tester were performed to compare the adherence properties between the contaminated and cleaned-up conditions. Furthermore, the British Pendulum Tester, Indirect Tensile Stiffness Method used to assess the mechanical behaviour of samples spilled with hazardous substances were carried out in a laboratory. The achieved trial field results demonstrated that rapid cleaning treatment can optimally restore skid resistance compared to untreated areas. Depending on the type of spill, the clean-up procedure leads to the complete skid resistance recovery in a short period. The prolonged presence of hazardous substances on asphalt samples causes decay of mechanical performances as evidenced by the laboratory tests
Quality assessment of recycled C&Ds’ materials compacted using Continuous Compaction Control
No full textEvaluation of bearing capacity is shifting towards enhanced Qc/Qa activities by means of non-destructive testing devices and/or roller integrated Continuous Compaction Control systems (CCC). The aim of this paper was to apply different types of compaction quality assessment criteria to C&D recycled materials compacted using an intelligent compactor equipped with CCC. Assessment criteria are based on the use of CCC measurements and/or independent spot-testing performed with deflectometric devices (Light Weight Deflectometer). Acceptance is based either on CCC results obtained over the compacted area and verified with direct LWD spot-tests, or, alternatively, on CCC proof-rolling measurements alone, for rapid quality control. A third criterion consists in calculation of a CCC target Stiffness Value worked out from a CCC-LWD correlation calibrated on a specific compacted section. Each criterion can be adopted as the single assessment to be performed; alternatively two or more options can be combined to increase acceptance reliability, depending on the importance of the construction or the variability of materials used
Experimental study on use of recycled polymer as modifier in mastic and asphalt mixture
No full textEnvironment wastes caused by technological and industrial development are increasing. Whereas natural resources and disposal area for those wastes are decreasing day to day. So, recycling and reuse of waste materials has become crucial in terms of protection of environment and economy. In this research, a new polymer coming from the recycling of mixed plastic wastes has been used as fibres to increase asphalt mixture mechanical properties. In order to evaluate the rheo-mechanical effects of this new polymer the multiscale approach has been applied, evaluating mastic and mixture properties. The study has been started from the Asphalt Concrete scale through Indirect Tensile Stiffness Modulus (ITSM) test and Repeated Load Axial (RLA) test, in order to obtain stiffness and permanent deformation resistance of the mixtures. The scale has been reduced from mixture to mastic, obtaining complex modulus and phase angle of mastics using Dynamic Shear Rheometer (DSR). The results confirm as the new polymer increases mixture bearing capacity and rutting resistance
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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