This paper has presented an analysis to compare the relative performance of four backcalculation algorithms in estimating the pavement slab elastic modulus Ec and the modulus of subgrade reaction k of concrete pavements. The LTPP database of deflection test data and measured pavement properties were used as the basis for assessing the relative suitability of different backcalculation algorithms for specific practical applications. The relative performance of four backcalculation algorithms were evaluated by comparing the backcalculated Ec and k against the corresponding measured values. The four algorithms examined in this study differ in the number of sensors and sensor configuration used in the backcalculation analysis, as well as their criteria for matching the calculated and measured deflections. ILLIBACK4 and ILLIBACK7 have the most stringent criteria in matching the weighted cross-sectional area of the measured deflection basin, followed by the LTTP best-fit method that matches the computed point deflections with the corresponding measured deflections. The NUSBACK has the most flexible requirement as it permits the selection of two most suitable deflection points for backcalculating each pavement property. The analysis presented in this paper illustrates that the choice of sensor configuration (i.e. the number of sensors included as well as the locations of the selected sensors) has significant effects on the performance of the backcalculation algorithms. Since the actual pavement system does not deform exactly in the manner described by the elastic theory, forced matching of the computed and measured deflection basins does not necessarily produce the best results in backcalculation analysis. This point has been illustrated by the analysis presented in this study. The stringent requirements imposed by the two ILLIBACK algorithms did not lead to better performance. The relatively superior performance of NUSBACK indicates that although the theoretical and measured deflection basins are not the same, it is possible to identify selected sensor deflections for backcalculation analysis and produce satisfactory results. A concept of deflection-pair backcalculation sweep using NUSBACK was also introduced. It serves to identify the most suitable deflection pair for backcalculation of a particular pavement property, and to provide a quality check on the presence of faulty sensor readings.


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    Title :

    Evaluation of backcalculation methods for nondestructive determination of concrete pavement properties


    Additional title:

    Bewertung von Rückrechnungsmethoden zur zerstörungsfreien Bestimmung der Eigenschaften von Betonstraßenbelägen


    Contributors:
    Setiadji, B.H. (author) / Fwa, T.F. (author)


    Publication date :

    2006


    Size :

    23 Seiten, 6 Bilder, 5 Tabellen, 12 Quellen


    Type of media :

    Conference paper


    Type of material :

    Storage medium


    Language :

    English