Reliability Analysis of Flexible Pavement Using First Order Method

Flexible pavement design is influenced by many design parameters such as (traffic characterization, pavement depths, structure materials and environmental conditions). To study the impact of variations in design parameters on pavement performance, several attempts have been achieved to add reliability concept to the mechanistic-empirical (M-E) design of pavements. In (M-E) design of pavements, the pavement life depends on subgrade rutting and fatigue cracking, considering them as independent failure patterns. The current design methodology used in many countries such as Egypt is ignoring the impact of temperature variation (despite its importance) on the pavement design. This research aimed to predict the pavement reliability due to variation in pavement design parameters especially temperature using the first-order reliability method (FORM) considering rutting and fatigue failures. Moreover, a comparison was performed between regressions models represented from different pavement agencies to recommend the most efficient one for Egyptian temperature. The results obtained that, considering design parameters variations (without temperature); the reliability based on US Army Corps method (91.64%) was the nearest one to the current design methodology in Egypt (91.0%). After adding temperature variations, the reliability was clearly affected where the regression model of Shell Research agency was the most appropriate one for all Egyptian temperature zones as it achieved the lowest error mean (-0.03) and the lowest error standard deviation (0.0011). Moreover, the air temperature of 28ºC was considered as the inflection point for pavement reliability-temperature curve in Egypt.