This paper reviews the backcalculation technique, focusing on the key assumptions of the method, including the necessary information regarding incubation. Find a library where document is available. highways department guidance notes on backcalculation of layer moduli and estimation of residual life using falling weight deflectometer test data. Backcalculations is an important method for reconstructing past rates of human immunodeficiency virus (HIV) infection and for estimating current prevalence of HIV infection and future incidence of acquired immunodeficiency syndrome (AIDS).
BACKCALCULATION SOFTWARE
The results of the study suggest that the algorithm can be effectively incorporated into backcalculation software for multilayer flexible pavements. The proposed seed modulus generation algorithm does not suffer from the location and pavement type transferability constraints of most regression-based seed modulus generation methods. In comparison, the corresponding improvements for the case of EVERCALC were less. It was found that the proposed seed modulus generation algorithm led to enhanced program performance of MICHBACK with respect to convergence characteristics and the accuracies of the backcalculated solutions. A comparison was made of the backcalculation program performance and the computed moduli of solutions obtained from internally generated seed moduli and those obtained from seed moduli generated by the proposed algorithm. An evaluation analysis of the effectiveness of the proposed procedure is presented by the use of two types of backcalculation software, MICHBACK and EVERCALC, and is based on measured and computed data for flexible pavement segments from the Long-Term Pavement Performance project. The proposed algorithm does not require any subjective judgment by the user. With the aim of providing useful guidance in the choice of seed moduli, a seed modulus generation algorithm, 2L-BACK, for multilayer flexible pavements based on a closed-form modulus backcalculation solution for two-layer flexible pavement structures was developed. However, as the internally generated seed moduli do not always produce satisfactory results, the use of user-input seed moduli is generally encouraged. Practically all backcalculation programs provide internally generated seed moduli for backcalculation analysis. The seed moduli chosen for backcalculation analysis of multilayer flexible pavements can have significant impacts on the performance of backcalculation software and, sometimes, the final solutions of the backcalculated moduli.
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Seed Modulus Generation Algorithm for Backcalculation of Flexible Pavement Moduli