Nemzetközi szemle: Május
Szupernehéz terhelési mozgások értékelésének elemző módszerei hajlékony burkolatokon
Analysis Procedures for Evaluating Superheavy Load Movement on Flexible Pavements
Szerző(k): E.Y. Hajj, R.V. Siddharthan, H. Nabizadeh, S. Elfass, M. Nimeri, S.F. Kazemi, D. Batioja-Alvarez, M. Piratheepan (University of Nevada USA)
Terjedelem: 122 oldal
The movement of superheavy loads (SHLs) has become more common over the years, since it is a vital necessity for many important industries, such as chemical, oil, electrical, and defense. SHL hauling units are much larger in size and weight compared to the standard trucks. SHL gross vehicle weights may be in excess of a few million pounds, so they often require specialized trailers and components with nonstandard spacing between tires and axles. Accommodating SHL movements requires the determination of whether the pavement is structurally adequate and involves the analysis of the likelihood of instantaneous or rapid load-induced shear failure. In this study, a comprehensive mechanistic-based methodology consisting of the following procedures was developed: segmentation of an SHL vehicle for analysis, subgrade bearing failure analysis, sloped-shoulder failure analysis, buried utility risk analysis, localized shear failure analysis, deflection-based service limit analysis, and cost allocation analysis. In addition, a comprehensive experimental program that included five fullscale pavement/soil testing experiments performed at a large-scale box facility was designed and carried out for the verification and calibration of a number of theoretically based procedures incorporated in the analysis approach. Supplementary numerical modeling as well as measured data from Accelerated Pavement Testing facilities provided additional verification of the procedures adopted in this study. The analysis procedures developed were then implemented into a user-friendly software package, SuperPACK (Superheavy Load Pavement Analysis PACKage), to evaluate SHL movements on flexible pavements. This report presents a summary of the analysis procedures developed for evaluating SHL movement on flexible pavements.
Előregyártott beton burkolat. A Szövetségi Útügyi Hivatal kutatási és technológiai értékelése
FHWA Research and Technology Evaluation: Precast Concrete Pavement
Szerző(k): Bucci, M. Keen, K. Coppinger, J. Condon (John A. Volpe National Transportation Systems Center USA)
Terjedelem: 52 oldal
This evaluation assesses the outcomes of the Federal Highway Administration’s (FHWA’s) investment in precast concrete pavement (PCP). The evaluation team determined the benefits and costs of individual PCP projects and, where possible, extrapolated findings from the data based on overall themes. Additionally, the evaluation team determined the outcomes and impacts of FHWA research, demonstrations, workshops, and related activities and developed recommendations to facilitate the continued adoption of the technology. FHWA’s efforts were found to be largely successful and contributory to the development and adoption of PCP. FHWA has overseen initial research and prototypes and has helped the use of PCP technology become routine in some States. PCP is an effective and efficient way to conduct roadway maintenance, repairs, and reconstruction. Benefits significantly exceed costs in high-volume areas or unique roadway sections that would lead to significant detours if closed for long periods of time. PCP also allows for innovative maintenance practices and cost savings, such as the reuse of concrete panels for temporary repairs.
Aszfalt burkolati rétegek felülről lefelé repedésének mechanikai-tapasztalati modellje
A Mechanistic Empirical Model for Top Down Cracking of Asphalt Pavements Layers
Szerző(k): R.L. Lytton, X. Luo, M. Ling, Y. Chen, S. Hu, F. Gu (The Texas A&M University System USA)
Terjedelem: 213 oldal
The project is required the development and synthesis of eight components: (a) laboratory testing of asphalt field cores for complex modulus gradient and master curve; (b) kinetics-based modeling of long-term field aging in asphalt pavements; (c) finite element computations of the J-integral at the crack tip; (d) use of the finite element program to develop full factorial sets of pavement data to construct Artificial Neural Network (ANN) models for the J-integral at the crack tip; (e) prediction of top-down cracking due to thermal loading based on the J-integral under thermal stresses; (f) develop a top-down crack initiation model and a crack growth model under traffic loading and environmental effect; (g) generation of a cumulative damage model to predict top-down cracking propagation; and (h) development and calibration of top-down cracking prediction model.
Mobiltelefon hálózati adatok felhasználása utazási viselkedési kutatásokhoz
The application of cellular network data for travel behavior research
Szerző(k): F.A. Gregersen, E.B. Lunke (Norwegian Centre for Transport Research)
Terjedelem: 32 oldal
This report is a literature review of the application of cellular network data from mobile phones for travel behavior research.
Újdonságok az aszfalt keverék tervezési eljárásokban
Innovations in Asphalt Mixture Design Procedures
Szerző(k): Fee, S. Buchanan, S. Cooper III, L. Mohammad, H. Ozer, I. Al-Qadi, F. Zhou, T. Bennert, J. Haddock, T. Aschenbrener (Transportation Research Board USA)
Terjedelem: 95 oldal
This E-Circular was developed from presentations made during the 95th Annual Meeting of the Transportation Research Board in a workshop titled Innovations in Asphalt Mix Design Procedures. The fundamentals of asphalt mix design are examined for improved durability and performance along with recent advancements in specifications and construction. Common themes include strategies that yield more binder into the mix with trials that modify the air void and void in mineral aggregate (VMA) requirements that complement the Superpave system. Methodologies to incorporate rejuvenators for increased reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) are presented. Performance testing ties together these approaches the concepts shown for balanced mix designs. The benefits of achieving adequate field compaction and comparisons of these innovative mix design and performance evaluations from field test sections are explored.
Aktív forgalomirányítás tervezési eszköze a mikroszimuláció és a dinamikus forgalmi ráterhelés kombinálásával
A Planning Tool for Active Traffic Management Combining Microsimulation and Dynamic Traffic Assignment
Szerző(k): S.D. Boyles, C.M. Walton, J. Duthie, E. Jafari, N. Jiang, A. Khani, J. Li, J. Osorio, V. Pandey, T. Rambha, C. Yahia (The University of Texas at Austin USA)
Terjedelem: 147 oldal
Active traffic management (ATM) strategies have been considered as a tool for congestion mitigation in the last few decades. They rely on real-time traffic observations to regulate the flow of traffic. This research focuses on developing tools for evaluating the effectiveness of ATM strategies for freeway corridors. The research efforts can be categorized into two parts. The first part performs a detailed microsimulation analysis for four ATM strategies commenting on their effectiveness under cases of recurring and non-recurring congestion and develops a hybrid microsimulation-DTA model to capture the combined microscopic and network-level impacts of an ATM strategy. The second part develops spreadsheet tools which are useful to predict effectiveness of an ATM strategy under different levels of data availability. Ramp metering, variable speed limits, and hard shoulder running are found effective on the Williamson County test network, whereas dynamic ramp control and freeway arterial coordinated operations do not lead to any significant improvement. We also find that ATM strategies can improve the performance over a corridor while simultaneously reducing the performance of frontage roads due to spillover effects. Our findings also indicate that a hybrid microsimulation-DTA model is useful for an accurate analysis. However, based on the network characteristics, changes in route choice patterns may/may not be significant. The regression models used in the spreadsheet tool in the second part provide a good fit to the simulation results and thus can be used as an initial tool for testing effectiveness of ATM strategies during planning stage.
Hézagolt betonburkolat tervezésének és építésének áttekintése
Jointed Plain Concrete Pavement Design and Construction Review
Szerző(k): Wehbe, R. Reid, J. Stripling, B. Edgar, H. Mahgoub, M. Underberg (South Dakota State University USA)
Terjedelem: 130 oldal
An experimental research study was conducted to develop optimized concrete mixtures for jointed plain concrete (JPC) pavements and field evaluation of newly constructed JPC pavement sections along South Dakota highways. Using South Dakota aggregates, different concrete mixtures were assessed for optimum workability, durability, and cost. The optimized mixtures incorporated 1.5″ aggregate top size and reduced cement content. Mixtures containing pea rock exhibited poor freeze-thaw durability. Mixtures with 1.0″ aggregate top size and 65/35 coarse-to-fine aggregate ratio exhibited low workability. A new laboratory technique that involves measuring the “specific work” of fresh concrete was developed to compare workability of different mixtures. Field data obtained from newly constructed JPC pavements demonstrated the following: thicker concrete pavement results in greater change in joint gap width, while the presence of asphalt underlayment results in lesser change in joint gap width; unsealed transverse joints allow for significantly higher moisture ingress than silicone sealed or hot-pour sealed joints; silicone sealed joints exhibited the least moisture ingress; treating the freshly placed JPC pavement with 1.5 times the normal amount of curing compound had a significant effect on maintaining pavement smoothness with time; high initial load transfer efficiency was achieved at joints with reduced dowel bar arrangements; and joint faulting was negligible across joints with either standard dowel bar configuration or reduced dowel bar configuration.
Biztonságosabb városi utcák. A városi közúti biztonság összehasonlító értékelése
Safer City Streets. Global Benchmarking for Urban Road Safety
Szerző(k): The International Transport Forum OECD
Terjedelem: 33 oldal
The International Transport Forum collected mobility and road safety data from 31 cities, the majority of which in Europe, 10 in the Americas and 2 in Oceania. Indicators were developed to evaluate, monitor and benchmark road safety outcomes. A network of road safety experts was developed in parallel to support data collection and to exchange experiences with road safety analysis and policy making. Members of this network met in Paris on 20-21 April 2017, in Brussels on 7-8 December 2017 and in Rome on 11-12 April 2018. Together, the global city-level road safety database and the network of road safety experts make up the Safer City Streets initiative. It is delivered by the International Transport Forum in partnership with the International Automobile Federation (FIA), and with support from the International Traffic Safety Data and Analysis group (IRTAD).