Nemzetközi szemle: November
A nedvesség károsító hatása meleg aszfalt keverékekre
Moisture Damage to Hot-Mix Asphalt Mixtures
Synopsis of a Workshop Transportation Research Board, USA
Terjedelem: 66 oldal
Asphalt concrete moisture damage is a widespread problem with distress mechanisms capable of stemming from multiple sources including materials selected, stockpile moisture contents, plant production, construction, and sustained elevated moisture levels under heavy traffic. Rapid deterioration of pavements occurs due to moisture damage, yet many key aspects of the problem are not fully understood and some of the behaviors that are better understood are not always monitored or controlled. Moisture damage practices vary between the auspices of different agencies. To provide a forum to improve resistance of asphalt concrete to moisture damage, a half day workshop was held at the 91st Annual Meeting of the Transportation Research Board in 2012. The workshop was organized to provide a global assessment of moisture damage from materials and construction through service. Test methods and theoretical aspects of moisture in relation to asphalt concrete were also considered. The workshop provided best practices, but also provided forums to discuss areas where improvement is needed. This Transportation Research E-Circular includes a synopsis of six presentations of the Moisture Damage to Hot-Mix Asphalt Mixtures Workshop.
Újszerű minőségbiztosítási rendszerek a közútépítésben
Alternative Quality Management Systems for Highway Construction
K. R. Molenaar, E. Kraft, Ch. Harper, D. Gransberg, N. West, G. Gad, D. N. Sillars, L. Harmon University of Colorado, Iowa State University, Oregon State University USA
Terjedelem: 322 oldal
This report is an extension to the NCHRP Guidebook on Alternative Quality Management Systems for Highway Construction. The research report documents the research process, data collection and analysis used to develop the guidebook. This intent of this research report is to provide more detailed information to individuals conducting future quality management research and state transportation agency (STA) engineers who are charged with implementing alternative quality management systems (QMS).
A közútépítés újszerű minőségbiztosítási rendszereinek kézikönyve
Guidebook on Alternative Quality Management Systems for Highway Construction
K. R. Molenaar, D. Gransberg, D. N. Sillars University of Colorado, Iowa State University, Oregon State University USA
Terjedelem: 93 oldal
This guidebook provides recommendations and tools to assist in developing quality management systems (QMSs) and assistance in creating a better definition of quality management in the context of alternative project delivery. The roles of owners and contractors in QMSs are changing, leading to variation in the roles and responsibilities of quality assurance organization (QAO). These range from the agency-dominated system of quality management associated with the traditional design-bid-build (DBB) method to design-build (DB)/public-private partnership (PPP) agreements where the responsibility for quality management is shared to varying degrees between the contractor and owner. This report will be valuable to highway construction engineers by facilitating the development of QMSs for evolving alternative project delivery methods.
Közös városi kerékpárhasználat New-Yorkban: az első két év tapasztalatai
Citi Bike: The First Two Years
S. M. Kaufman, L. Gordon-Koven, N. Levenson, M. L. Moss Rudin Center for Transportation Policy and Management USA
Terjedelem: 24 oldal
New York City launched Citi Bike, the largest bike share program in the United States, in May 2013. This study examines the ﬁrst two years of Citi Bike and its role in New York City mobility. Citi Bike’s station connection to public transportation hubs and station density are major factors in the system’s high ridership and use. Seventy-four percent of Citi Bike stations are within a ﬁve-minute walk of a subway station entrance, providing a “last mile” solution for transit commuters. The system’s greatest challenges are expanding and diversifying its customer base while also rebalancing the number of bicycles available at high-demand stations. Citi Bike has become an integral part of New York’s transportation culture, even though it serves a limited geographic area. This report addresses those challenges and recommends strategies for the future.
A dinamikus tengelyterhelések és azok úthálózatra gyakorolt hatásainak elemzése
Analysing Dynamic Wheel Loading and its Effects on the Network a letöltéshez ingyenes regisztráció szükséges
B. Wright, Ch, Blanksby Austroads, Australia
Terjedelem: 87 oldal
This interim report is the third of three deliverables in the 2013–14 and 2014–15 project years for Austroads project AT1733, Analysing Dynamic Wheel Loading and its Effects on the Network. The purpose of the project is to quantify the impacts of dynamic wheel loads applied by vehicles to pavement surfaces and bridges. As documented in the report, the project has implemented changes in approach to overcome limitations in previously trialled models for linking vehicle/road characteristics and dynamic wheel loads. In particular, a physical dynamics model has been implemented to replace previous statistical models, and provide a more reliable and accurate link between wheel loads and road profile, and enable calculations of spatial repeatability. This approach, and the selected dynamic parameters to study, was supported through a comprehensive literature review. A test program, specifically designed to collect data to support this revised modelling approach, was also carried out successfully.
Folyamatos hídvizsgálati pilot rendszer megvalósítása az Iowa Falls-i Arch Bridge ívhídon
Implementation of a Pilot Continuous Monitoring System: Iowa Falls Arch Bridge
B. M. Phares, J. Dahlberg, N. Burdine Bridge Engineering Center, Iowa State University, USA
Terjedelem: 71 oldal
The goal of this work was to move structural health monitoring (SHM) one step closer to being ready for mainstream use by the Iowa Department of Transportation (DOT) Office of Bridges and Structures. To meet this goal, the objective of this project was to implement a pilot multi-sensor continuous monitoring system on the Iowa Falls Arch Bridge such that autonomous data analysis, storage, and retrieval can be demonstrated. The challenge with this work was to develop the open channels for communication, coordination, and cooperation of various Iowa DOT offices that could make use of the data. In a way, the end product was to be something akin to a control system that would allow for real-time evaluation of the operational condition of a monitored bridge. Development and finalization of general hardware and software components for a bridge SHM system were investigated and completed. This development and finalization was framed around the demonstration installation on the Iowa Falls Arch Bridge. The hardware system focused on using off-the-shelf sensors that could be read in either “fast” or “slow” modes depending on the desired monitoring metric. As hoped, the installed system operated with very few problems. In terms of communications—in part due to the anticipated installation on the I-74 bridge over the Mississippi River—a hardline digital subscriber line (DSL) internet connection and grid power were used. During operation, this system would transmit data to a central server location where the data would be processed and then archived for future retrieval and use. The pilot monitoring system was developed for general performance evaluation purposes (construction, structural, environmental, etc.) such that it could be easily adapted to the Iowa DOT’s bridges and other monitoring needs. The system was developed allowing easy access to near real-time data in a format usable to Iowa DOT engineers.
Aktív forgalmi menedzsment stratégiák fejlesztése Minnesota gyorsforgalmi folyosóin
Development of Active Traffic Management Strategies for Minnesota Freeway Corridors
E. Kwon and C. Park University of Minnesota, USA
Terjedelem: 55 oldal
In this study, the effectiveness of the I-35W variable advisory speed limit system on the improvement of the traffic flow was evaluated with the real traffic data. The analysis results indicate there was significant reduction in the average maximum deceleration and also the traffic time reliability was substantially improved during a peak hour period. Based on the assessment results, an enhanced version was developed to be able to reflect more effectively the time-variant road traffic conditions in determining the variable speed limits in real time. The coordinated adaptive metering strategy, developed in the previous phase of this research, is also enhanced and implemented in the field in this research. The field test results of the new metering system with the 100 NB corridor indicate substantial improvements in both the mainline and ramp traffic performance compared with those from the old stratified algorithm.
Alacsony hőmérsékletű aszfaltok hideg repedési ellenállásának értékelése
Evaluation of Low Temperature Cracking Resistance of WMA
Sang-Soo Kim, Munir Nazzal, Ala R. Abbas, Moses Akentuna, and Mir Shahnewaz Arefin Ohio University, USA
Terjedelem: 121 oldal
The use of water injection foamed warm mix asphalt (WMA) has increased rapidly in the State of Ohio for environmental and economic benefits. The purpose of this study was to determine the low temperature cracking potential of WMA in comparison to the conventional hot mix asphalt (HMA) and to determine factors affecting the low temperature performance of WMA and HMA. To achieve these objectives, the low temperature performance of WMA and HMA was determined using the thermal stress restrained specimen test (TSRST) and asphalt concrete cracking device (ACCD). The coefficient of thermal expansion/contraction (CTE) of asphalt mixes was also determined using the Ohio CTE device. In addition, the low temperature performance of asphalt binder was determined using the bending beam rheometer (BBR) and the asphalt binder cracking device (ABCD). Laboratory produced WMAs and HMAs had similar low temperature performance while field WMAs showed an improved low temperature performance. The low temperature performance grading procedure based on BBR graded polyphosphoric acid (PPA) modified binders to colder temperatures than the grades estimated from ACCD mixture test. For SBS modified binders the low end BBR PG grade temperatures were warmer than the grades estimated from ACCD mixture test. This incorrect low temperature BBR PG grading seemed due to changes in the binder strength due to modification. PPA modification tends to reduce the strength and SBS modification tends to increase the strength. ABCD grading temperatures were in better agreement with the ACCD mixture cracking temperatures than the BBR PG grading. The inclusion of 15% recycled asphalt pavement (RAP) and 5% recycled asphalt shingle (RAS) separately in the asphalt mixes resulted in 1 to 2°C colder ACCD cracking temperature than the control mix without RAP or RAS. The effects of RAP and RAS on CTE, strength and the rate of thermal stress development were different, indicating different blending mechanisms with the virgin binder. The use of a high CTE aggregate with 8.4 µε/°C, in comparison to a low CTE aggregate with 4.2 µε/°C, increased mix CTE by about 2 µε/°C and resulted in 1 to 2°C colder ACCD cracking temperature. Binder content did not have a significant effect on the ACCD cracking temperature while a low compaction effort resulted in a colder cracking temperature by producing thicker asphalt binder film between aggregate particles. However, the low level compaction for thicker asphalt film will adversely affect the rutting, fatigue, and stripping resistance of asphalt pavements.