Evaluation of Dowel Bar Alignment and Effect on Long-term Performance of Jointed Pavement PDF Download
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Author: Tyson Rupnow
Publisher:
ISBN:
Category : Dowels
Languages : en
Pages : 29
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Author: Tyson Rupnow
Publisher:
ISBN:
Category : Dowels
Languages : en
Pages : 29
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Author: Shreenath P. Rao
Publisher:
ISBN:
Category : Pavements, Concrete
Languages : en
Pages : 120
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Book Description
Magnetic imaging tomography (MIT) scanning is a nondestructive method for measuring the alignment of dowels placed at transverse joints of jointed plain concrete pavements (JPCPs). Several highway agencies across the United States have adopted specifications for dowel alignment, with many using the joint score measure. However, this measure was developed intuitively and not based on any laboratory or field tests. National Cooperative Highway Research Program (NCHRP) Report 637 provides a methodology to determine an equivalent dowel diameter measure based on dowel misalignment (Khazanovich et al. 2009). This procedure was developed from laboratory tests and with limited field validation. The relationship between dowel misalignment and the performance of JPCP is unclear, but understanding it is imperative for developing construction guidelines. This report presents results of MIT scanning data collected on Long-Term Pavement Performance (LTPP) test sections and data analysis to assess the effects of dowel misalignment on JPCP performance. As part of this study, MIT scanning was performed on 121 Specific Pavement Studies-2 and 3 General Pavement Studies-3 test sections. Dowel alignment parameters, joint score, and equivalent dowel diameter were calculated as part of the analysis. Statistical analysis was performed to determine any relationship between the joint score and cracking and between the joint score and spalling. The analysis did not indicate any definitive relationship between the joint score and cracking or the joint score and spalling within the analysis range for most States, although some effect was observed for three States. This lack of relationship does not mean severely misaligned dowels have no effect on pavement performance, particularly localized distresses. Analysis of the equivalent dowel diameter as a measure of dowel misalignment for use with AASHTOWare® Pavement ME Design software suggests that using the equivalent dowel diameter is a less-biased estimator of long-term load transfer efficiency (LTE), as modeled using AASHTOWare Pavement ME Design, than using the actual dowel diameter, suggesting a relationship between dowel misalignment and long term LTE (AASHTO 2014). However, there is considerable scatter in the LTE modeled using AASHTOWare Pavement ME Design versus actual LTE. The remaining bias and scatter suggests that the models (i.e., equivalent dowel diameter and LTE in AASHTOWare Pavement ME Design) could potentially be improved using data collected as part of this study.
Author: H. Thomas Yu
Publisher:
ISBN:
Category : Pavements, Concrete
Languages : en
Pages : 48
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This report evaluates and documents the dowel alignment in 16 different in-service pavements from 9 different U.S. states. The quality of dowel bar alignment was evaluated in terms of the percentage of bars at various levels of misalignment and joint score. In general, the quality of dowel alignment in typical in-service pavements is very good. However, misaligned bars were found even in the section with the best overall dowel alignment. Projects with a significant number of misaligned bars performed well without showing any signs of distress after 8 or more years of service under heavy traffic. The findings suggest that a limited amount of misaligned bars in concrete pavement joints may be tolerable, and that a few randomly distributed locked joints do not adversely affect pavement performance. Another important finding of this study is that poor dowel alignment may not necessarily manifest into distresses in the short term (within a few years of construction). Further research is needed to determine threshold values of dowel alignment for free joint movement, as well as the conditions that can adversely affect pavement performance.
Author: Sara Jennifer Somsky
Publisher:
ISBN:
Category :
Languages : en
Pages : 302
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In jointed concrete pavements, dowel bars are typically used to transfer loads between adjacent slabs. These dowels are typically made of steel and are spaced 12 inches on center for the full length of a transverse joint. The objective of this research was to evaluate the impact of the number of dowel bars and dowel location on pavement performance and joint performance. Consequently, four dowel arrangements were evaluated: 1) zero dowels, 2) three dowels in the outside wheel path, 3) four dowels in the outside wheel path, and 4) full basket of dowels (twelve). In addition, two test sites were prepared with two different subgrades, one with a compacted soil subgrade (Rural site) another with a built up asphalt surface treatment subgrade (Urban site). Evaluations of the test sections were performed biannually (early fall or late summer and early spring) over a five-year testing period. In addition, a soil investigation was performed using in-situ soil classification from soil borings and consultation of US Department of Agriculture soil survey. Biannual evaluation of both the Urban and Rural sites consisted of: 1) visual distress surveys, 2) joint opening measurements, 3) joint faulting measurements, and 4) deflection measurements using an Iowa DOT (Department of Transportation) Road Rater. Analysis of the biannual testing indicated that the stiffness of a subgrade magnifies the effect of dowel arrangement on a pavement. It was recommended for pavements with a weak subgrade (dynamic k-values less than 200) to use the standard (full) dowel compliment. For pavements with a strong/stiff subgrade (dynamic k-values greater than 220), three or four dowels in the outside wheel path will suffice. Additional investigation is needed to recommend a dowel bar arrangement for moderately weak to moderately strong subgrades, possibly with dowels in the inside wheel path.
Author: Basim Hassan Shnawa Al-Humeidawi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category : Electronic book
Languages : en
Pages :
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Author: Shad M. Sargand
Publisher:
ISBN:
Category : Pavements
Languages : en
Pages : 452
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Author:
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ISBN:
Category : Air travel
Languages : en
Pages : 586
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 174
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Author:
Publisher:
ISBN:
Category : Dowels
Languages : en
Pages : 52
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As truck traffic on Iowa secondary roads has increased, engineers have moved to concrete pavements of greater depths. Early designs included thickened edge pavements and depths of seven inches or greater. The designs typically did not have load transfer devices installed in the transverse joints and relied on aggregate interlock for this purpose. In some cases, aggregate interlock was not adequate to deal with the soils and traffic conditions and faulting of the joints has begun to appear. Engineers are now faced with the need to install or retrofit load transfer in the joints to preserve the pavements. Questions associated with this decision range from the type of dowel material to dowel diameter, spacing, number of bars, placement method, and construction techniques to be used to assure reduction or elimination of faulting. Buena Vista County constructed a dowel bar retrofit project on one mile of road. The plan called for addition of the dowels (2, 3, or 4) in the outer wheel path only and surface grinding in lieu of asphalt overlay. The project included the application of elliptical-and round-shaped dowels in a rehabilitation project. Dowel material types included conventional epoxy-coated steel and fiber-reinforced polymer. This work involved the determination of relative costs in materials to be used in this type of work and performance of fiber-reinforced polymer (FRP) and elliptical-shaped steel dowels in the retrofit work. The results indicate good performance from each of the bar configurations and use the results of ride and deflection testing over the research period to project the benefits that can be gained from each configuration vs. the anticipated construction costs. The reader is cautioned that this project could not relate the number of dowels required to the level of anticipated truck traffic for other roads that might be considered.
