Application Of Reliability Concept In Highway Pavement Design In Egypt

Recent studies and observations conducted on the behavior of highwaypavements, have emphasized the variabilities in the magnitude and distribution of traffic loading, in the properties of pavement materials, and in the enviromnental conditions. These variabilities will inevitably result in some degree of randomness and uncertainties in the response of pavement structures to these factors, which should also be accounted for in the evaluation of performance of the pavement structures.The rapid increase In the number of Equivalent Single Axle Loads(ESAL) passing over the pavement surface and the high construction andmaintenance costs emphasis the need for a rational method of analysis anddesign based on a tme representation and understanding of the contributionwhich each element of the pavement structures and the surroundingenvironment makes to the overall deviation of pavement performance.Traditionally, the uncertainty of prediction of the future behavior ofconstructed facilities is accounted for by including safety factors in designs.The effectiveness of these safety factors varies with the degree of variation of the parameters they modify. The use of higher safety factors when one is less certain (or- when the consequences of loss are greater) is an implicit recognitionof this fact. In ’many cases, however, there can be substantial overdesign andmisallocation of resources because safety factors are too large for the actual uncertainties involved.