Browsing by Subject "Falling weight deflectometer"

Now showing 1 - 4 of 4
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    Delineation of the Stiff Layer from FWD Measurements
    (Minnesota Department of Transportation, 2001-10) Guzina, Bojan; Cao, Dongwei
    The Falling Weight Deflectometer (FWD) is a widely used non-destructive test device for estimating the pavement stiffness properties. However, the conventional elastostatic interpretation of FWD measurements is generally associated with a number of inconsistencies. The purpose of this project is to develop a reliable and effective dynamic backcalculation method capable of estimating the location and properties of the permanent or seasonal stiff layer (as well as other pavement stiffness properties) from FWD measurements. The backcalculation method is implemented in the form of a user-friendly software that allows unedited deflection time histories from the FWD test to be used as an input to the back-analysis. The backcalculation scheme developed in this study is based on the Artificial Neural Network (ANN) approach and employs a three-dimensional multilayer viscoelastic dynamic model as a predictive tool.
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    Implementation of Pavement Evaluation Tools
    (Minnesota Department of Transportation, 2013-11) Tang, Shuling; Guzina, Bojan; Labuz, Joseph
    The objective of this project was to render the Falling Weight Deflectometer (FWD) and Ground Penetrating Radar (GPR) road assessment methods accessible to field engineers through a software package with a graphical user interface. The software implements both methods more effectively by integrating the complementary nature of GPR and FWD information. For instance, the use of FWD requires prior knowledge of pavement thickness, which is obtained independently from GPR.
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    Resilient Modulus Development of Aggregate Base and Subbase Containing Recycled Bituminous and Concrete for 2002 Design Guide and Mn/Pave Pavement Design
    (Minnesota Department of Transportation, 2007-06) Westover, Thomas; Labuz, Joseph; Guzina, Bojan
    The primary objective of this study was to quantify stiffness (resilient modulus) of aggregate base containing recycled asphalt and concrete pavements. After a survey of other state's specifications and implementation guidelines, Minnesota recycling projects were selected based on the availability of laboratory resilient modulus (MR) tests and field measurements from FWD. The projects were County State Aid Highway 3, Trunk Highway 23 and Trunk Highway 200. Based on the results of a parametric study, it was found that traditional peak-based analysis of FWD data can lead to significant errors in elastostatic backcalculation. A procedure for extracting the static response of the pavement was formulated and implemented in a software package called GopherCalc. Laboratory resilient modulus measurements were compared with moduli backcalculated from the FWD data. The FWD data was analyzed using conventional (peak-based) and modified (FRF-based) elastostatic backcalculation (Evercalc) as well as a simplified mechanistic empirical model called Yonapave. Laboratory values from sequences in the MR protocol that produced a similar state-of-stress were used. Additionally, a seasonal analysis of FWD test data revealed a significant increase in stiffness when the pavement is in the frozen state.
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    Statewide Statistical Subgrade Characterization
    (Minnesota Department of Transportation, 1995-06) Barnes, Randal J.; Jankovic, Igor; Colom, David
    This report presents a detailed statistical analysis and graphical presentation of more than 120,000 subgrade modulus values from Minnesota state roads and highways. These subgrade modulus values are based on Falling Weight Deflectometer measurements collected by the Minnesota Department of Transportation between 1983 and 1993. The report gives a one-page summary for each road in each district where measurements exist. This summary page contains a plot of the modulus versus the reference post, modulus versus year when a measurement is collected, modulus histogram, and a number of state-wide summaries. The one-page summaries are accompanied by a number of district and state-wide summaries, and nomograms for the selection of sample spacing, to form the state of Minnesota subgrade modulus Atlas. In addition to this report, a Microsoft Windows-based computer program, the Minnesota Subgrade Modulus Atlas--Online, allows for the detailed analysis of the subgrade modulus along state roads and highways. This analysis can be carried out on a state-wide scale, on a small project scale of less than one mile, or any scale in between. "This electronic form of the Atlas can be easily upgraded as additional measurements become available.