This approach is computationally efficient, and when the depths of the layers are known, and their properties are largely homogeneous with depth, the procedure is effective in backcalculating layer properties. The traditional method for interpreting the FWD data to backcalculate structural pavement properties, involves extracting the peak deflection from each displacement trace of the sensors (deflection basin) and matching it through an iterative optimization method to the deflections predicted by a static model of the pavement. Deflection time histories are gathered by an array of sensors placed at several nearby locations. The FWD backcalculation is mathematically an inverse problem that could be solved with either a deterministic or a probabilistic approach. The excitation produced by the loading sets off waves in the pavement and underlying soil. Investigate the effect of the inputs used in the backcalculation process on the backcalculated modulus values. Development of ANN-GA Program for Backcalculation of Viscoelastic and Nonlinear Pavement Moduli under FWD Testing by Hao Wang, Ph.D and Maoyun Li. In the FWD test, a large weight is raised off the ground and dropped onto a rubber loading pad creating an impulse load representative of the real loading imposed by heavy traffic on the pavement.
The variation in resilient modulus was greater in the layers of the subgrade soil (−33 to +83%) and the unbound granular materials (−42 to +80%).The Falling weight deflectometer test (FWD) is a commonly used method for the evaluation of the structural performance of pavement systems. This influence was less significant in the case of asphalt concrete layers (☒5%). It was concluded, in general, that FWD uncertainty could have an important influence on the layers modulus obtained from back-calculations. A parametric study was performed considering the back-analysis of different asphalt pavements with regard to layer thickness and resilient modulus (unbound granular and asphalt concrete layers, including subgrade). Based on a proficiency test (PT) involving testing devices from different manufacturers, the objective of this study is to analyze the influence of FWD uncertainty on the back-calculated flexible pavement and foundation layers moduli. Inverse analysis of FWD measurements-back-calculation-is a common process for obtaining the pavement layer moduli, including the subgrade soil, which are useful for estimating remaining pavement life for overlay design purposes. With deflection time histories from a typical FWD test, it was possible to backcalculate the relaxation modulus curve, E(t), up to about t 10 1 s and the complex modulus curve. The use of Falling Weight Deflectometer (FWD) data to backcalculate. The Falling Weight Deflectometer (FWD) is one of the most important non-destructive tests (NDT) used for pavement structural evaluation based on deflection measurements. The method uses a layered viscoelastic forward algorithm in an iterative backcalculation procedure for linear viscoelastic characteristics of asphalt pavements. Kenlayer Based Pavement Backcalculation Moduli Using Artificial Neural Networks.
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