Kengo Obama

TA-METHOD AND PAVEMENT DEPRECIATION LIFETIME ERROR

In the current asphalt pavement design method (hereinafter called the TA method), the thickness of each pavement layer is determined based on the specified CBR (California bearing ratio) for the subgrade and the TA value (equivalent thickness) calculated from the total 10-ton conversional number of axes. However, as the highly functional pavement has been introduced for the surface layer, the deterioration conditions of asphalt pavements have changed considerably since the design method and standards were produced, and so the authors doubt the practical appropriateness of the design based on the TA method. In this study, the error in deterioration lifespan due to the TA method is analyzed. In detail, a mixed Markov deterioration hazard model is estimated by using the FWD (falling weight deflectometer) inspection data targeted at expressways. By using hazard rate and heterogeneity parameter, the road spans that have unusual deterioration rates are extracted, and the relations between these road spans and the factors that are not considered in the TA method are discussed. 現行のアスファルト舗装設計手法（以下，TA法）では，舗装各層の厚さは路床の設計CBRと総通過10トン換算軸数から定めたTA値（等値換算厚）に基づいて決定されている．しかしながら，表層の高機能舗装化に伴い，設計手法や設計基準が作成された当時と比較して，アスファルト舗装の劣化環境は大きく異なっており，実務においてTA法に基づく設計の妥当性が疑問視されてきている．本研究ではTA法を採用した場合に生じる劣化寿命誤差について分析する．具体的には，高速道路を対象としたFWD調査データを用いて混合マルコフ劣化ハザードモデルを推定する．ハザード率と異質性パラメータの推定値を用いて劣化速度が特異な道路区間を抽出し，それらの道路区間とTA法において考慮されなかった要因との関係について分析する．

Local mixture hazard model: A semi-parametric approach to risk management in pavement system

One of the core techniques for the Pavement Management Systems (PMS) is the deterioration hazard model. The hazard models stochastically forecast the deterioration progresses of pavement based on its historical performance indicators over time. This paper introduces a class of hazard models, which consider the heterogeneity factors by a local mixing mechanism. Special attention is paid to the formulation of transition probability of condition state, which is subjected to follow Markov chain. The paper further introduces optimization approach for selecting best repair strategy based on discounted life cycle cost analysis. The application of the model targets to minimize exposing risks to road administrators. The usefulness and practicability of the model are examined through life cycle costs evaluation with real data of Vietnamese highway system.