Reliability and risk analysis for overlay designing of flexible pavements

In this research a reliability-based method is proposed for the overlay design of flexible pavement. AASHTO’s method was used to compare with the proposed approach. According to the AASHTO procedure, the required overlay thickness was approximately half of that determined using the proposed method with an equal reliability level, while maintaining an equal reliability level pavement design based on the AASHTO procedure is more vulnerable. The proposed approach presented in this research can not only supplement the AASHTO procedure, but also enhance other pavement design methods in terms of reliability. In the following sections, various reliability methods are compared. According to the sampling method with a higher probability of failure than the first-order reliability method, the required overlay thickness is determined resulting in a more conservative overlay thickness. To validate and assess the accuracy of this method in Rtx software, the Monte Carlo simulation was performed using the R programming language. Through sensitivity analysis, it was concluded that the uncertainty associated with variables r₅, MR and SN_eff has the most significant impact on pavement reliability level. Therefore, it is essential to collect data related to these variables more carefully for future research. Using the proposed method, it becomes possible to choose the desired reliability level based on overlay thickness and costs. Consequently, pavement maintenance and repair can be performed optimally and economically.