EVALUATION OF RIGID PAVEMENT OVERLAY DESIGN PROCEDURE, DEVELOPMENT OF THE OAR PROCEDURE

A review and evaluation of existing rigid pavement overlay design procedures, including the ARE procedure (DOT-FH-11-8544) resulted in a fully computerized rational method for the design of overlays for rigid pavements. Although the reflection cracking model is a slight simplification of the ARE model, the overlay design presented herein represents a new concept in overlay design in that the concept of progressive failure of component layers is considered. The thickness of overlay is determined from the consideration of protecting the surface layer from fatigue failure while allowing lower layers (old pavement, bondbreaker layer) to fail during the design life. The progressive failure concept results in thinner overlays than would be derived from previous concepts of preventing further fatigue damage to the existing pavement. Both flexible and rigid overlays can be specified; the rigid overlays may be bonded or unbonded, and either jointed or CRC. The fatigue cracking distress function has been developed from the AASHO Road Test data, taking into consideration material variability at the various sections, and represents the best correlation of the Road Test results of all previous models. Stress analysis is done using elastic layer theroy with edge and corner load adjustment factors developed using a plate on multilayer elastic solid foundation program, consequently program execution is very fast (a few seconds on most mainframes). NDT testing (any device that measures deflection) or laboratory test results may be used in support analysis. The OAR procedure has been applied to several pavements in different parts of the U.S. with excellent correlation in performance prediction. Data input to the program is simple and fast, and the report contains instructions on development of input data with a minimum of testing. (FHWA)