Abstract
Variability of pavement design parameters has always been a concern to pavement designers and highway agencies. A robust pavement design should take into account the variability of the design inputs and its impact on the reliability of the design. In this study, the variability effect of thickness and stiffness of pavement layers was investigated. The variability of these parameters was described by their mean values, standard deviations and probability distribution functions. Monte Carlo Simulation method was utilised to incorporate variability of the design parameters and to construct the probability distribution function of the outputs. KENLAYER software was used to calculate pavement response at predetermined critical locations; pavement reponse was then used to predict pavement performance regarding permanent deformation, bottom-up and top-down fatigue cracking by using the mechanistic empirical pavement design guide (MEPDG) models. A Matlab code was developed to run that analysis and obtain the probability distribution function of pavement performance indicators over time. It was found that the variability of pavement layer thickness and stiffness has a significant impact on pavement performance. Also, it was found that not only the mean of the predicted performance indicators is increasing over time, but the variance of these indicators is also increasing. This means that pavement condition cannot be described by the mean values of the indicators but by the probability distribution function which can describe pavement condition at any reliability level.
Highlights
The concept of incorporating variability of pavement design variables in pavement analysis and design was first introduced by Darter and Hudson (1973)
The reliability principle was included as a part of AASHTO (1986) and AASHTO (1993) design guides; it was defined as the degree of certainty that a pavement designer adds to assure that the designed pavement maintains a certain level of serviceability over the design period
Summary and Conclusions Variability associated with pavement design parameters has always been a concern to pavement designers and highway agencies
Summary
The concept of incorporating variability of pavement design variables in pavement analysis and design was first introduced by Darter and Hudson (1973) They stated that due to the stochastic nature of pavement design parameters, a probabilistic design approach that takes into account the inherent variability and uncertainty of those parameters must be implemented in order to improve the reliability of the pavement design process. The reliability principle was included as a part of AASHTO (1986) and AASHTO (1993) design guides; it was defined as the degree of certainty that a pavement designer adds to assure that the designed pavement maintains a certain level of serviceability over the design period Such as ESALR=ESAL50%+SE×ZR where ESAL50% is the predicted number of load application at 50% reliability, SE is the standard error, ZR is the standard normal deviate, and ESALR is the predicted number of load application based on the desired reliability level. A reliability factor that can be selected based on the road type was developed which merely meant to assure that the designed Equivalent Single Axle Load (ESAL) exceeds the expected ESAL
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