Browsing by Subject "Falling weight deflectometers"

Now showing 1 - 4 of 4
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    Allowable Axle Loads on Pavements
    (Minnesota Department of Transportation Research Services Section, 2010-12) Bly, Peter; Tompkins, Derek; Khazanovich, Lev
    This report documents the development of a procedure to determine the structural adequacy and need of seasonal axle load restrictions for Minnesota low-volume roads. This procedure has been implemented into a new program, TONN2010. Since it is anticipated that the results of this study will be widely used by Mn/DOT, city, and county engineers, as well as consulting engineers involved in analysis of the falling weight deflectometer (FWD) data collected by the transportation agencies, an emphasis was made on development of a simple, easy to implement procedure. To simplify the procedure’s implementation, the number of inputs was minimized. TONN2010 utilizes pavement layer thicknesses, FWD deflection basins, air temperature of the previous day, pavement surface temperature at the time of testing, pavement location, and anticipated traffic. All the inputs required by TONN2010 can be easily obtained by the user. Using these inputs, TONN2010 proceeds to 1) backcalculate layer moduli using the backcalculation procedure developed in this study, 2) adjust the backcalculated moduli using MnPAVE temperature and seasonal adjustment factors, and 3) estimate pavement axle load capacity by mechanistic-empirical analysis. In addition to detailing TONN2010, the report further describes selection of the damage models, development of the backcalculation design procedure, determination of the critical structural responses, development of new structural rating indexes, and finally the calibration and validation of the proposed procedure.
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    Development and Simulation Software for Modelling Pavement Response at Mn/ROAD
    (1994) Zhang, Zhonglan; Stolarski, Henryk K.; Newcomb, David E.
    This report presents the development of simulation software for modelling dynamically loaded pavement response. The analysis is carried out by employing the finite element method and by integrating the resulting discrete equations of motion through the central difference method. The lower pavement layers (base, subbase and subgrade) are assumed to be elasto-plastic and are described by using the flow theory of plasticity. The mapped infinite elements are used instead of viscous boundaries to mitigate the wave reflection from the boundaries of the model. The predicted pavement responses are compared with the experimental results obtained by a Falling-Weight Deflectometer (FWD). Dowel bar load transfer mechanism is also analyzed.
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    Structural Evaluation of Asphalt Pavements with Full-Depth Reclaimed Base
    (Minnesota Department of Transportation, 2012-12) Tang, Shuling; Cao, Yuejian; Labuz, Joseph F.
    Currently, MnDOT pavement design recommends granular equivalency, GE = 1.0 for non-stabilized full-depth reclamation (FDR) material, which is equivalent to class 5 material. For stabilized full-depth reclamation (SFDR), there was no guideline for GE at the time this project was initiated (2009). Some local engineers believe that GE of FDR material should be greater than 1.0 (Class 5), especially for SFDR. In addition, very little information is available on seasonal effects on FDR base, especially on SFDR base. Because it is known from laboratory studies that SFDR contains less moisture and has higher stiffness (modulus) than aggregate base, it is assumed that SFDR should be less susceptible to springtime thawing. Falling Weight Deflectometer (FWD) tests were performed on seven selected test sections on county roads in Minnesota over a period of three years. During spring thaw of each year, FWD testing was conducted daily during the first week of thawing in an attempt to capture spring thaw weakening of the aggregate base. After the spring thaw period, FWD testing was conducted monthly to study base recovery and stiffness changes through the seasons. GE of SFDR was estimated using a method established by MnDOT using FWD deflections, and the GE of SFDR is about 1.5. The value varies from project to project as construction and material varies from project to project. All the materials tested showed seasonal effects on stiffness. In general, the stiffness is weaker in spring than that in summer and fall.
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    Toward the development of pavement-specific structural synthetic fibers
    (Minnesota Department of Transportation, 2024-06) Barman, Manik; Sabu, Rohith; Sharma, Pranav; Janson, Austin
    Thin fiber reinforced concrete (FRC) pavements and overlays can be economical for low- and moderate-traffic volume roads. Due to insufficient concrete cover thickness, thin concrete pavements or overlays cannot accommodate dowel bars that are typically used in conventional thick concrete pavements. The critical distress for such applications is the transverse joint faulting because of the lack of joint load transfer between the concrete slabs. The currently available synthetic structural fibers can contribute to joint performance to a certain extent. However, as pavements experience significant slab contraction and expansion and carry both wheel and environmental loads, there is a need to design and develop fibers that will provide high joint performance and help mitigate transverse joint faulting when used at an affordable dosage. The overall goal of this study is to develop pavement-specific fibers that will yield the needed joint performance benefits to achieve the intended design life. The study is being conducted in two phases. This report is written for Phase 1 of the study. The study started with a literature review, followed by a finite element analysis, falling weight deflectometer (FWD) data analysis, and laboratory testing of fiber reinforced concrete and individual fibers embedded in concrete. The finite element results and FWD data were amalgamated to quantify the possible joint load transfer of the base layer and foundation, aggregate interlocking, and the needed contribution from the structural fibers. A procedure was established to account for the contribution of the fibers. A new parameter, namely, modulus of fiber support, was introduced to evaluate the stiffness of the fibers that participate in joint load transfer. Notably, a laboratory approach is identified to determine the modulus of fiber support, which can help determine the optimum fiber dosages as well as design and test the pavement-specific fibers in the future phase of the study.