Analysis of structural behavior of AASHO road test rigid pavements

THE STUDY WAS CONDUCTED TO EXAMINE EXISTING THEORIES FOR STRUCTURAL BEHAVIOR OF RIGID PAVEMENTS IN VIEW OF THE LARGE AMOUNT OF CONTROL FIELD PERFORMANCE DATA COLLECTED DURING AASHO ROAD TEST. THE STUDY IS CENTERED AROUND TWO PRINCIPLE INDICATORS OF RIGID PAVEMENT PERFORMANCE; STRESSES IN THE PAVEMENT SLABS AND PAVEMENT DEFLECTIONS UNDER LOAD. ATTENTION IS ALSO GIVEN TO THE PATTERNS OF SLAB CRACKING AND FAILURE UNDER THE VEHICULAR TRAFFIC. A CRITICAL REVIEW IS PRESENTED OF EXISTING THEORIES OF STRUCTURAL BEHAVIOR OF RIGID PAVEMENTS. SIMPLE ANALYTICAL EXPRESSIONS FOR EVALUATION OF THE COEFFICIENT OF SUBGRADE REACTION IN TERMS OF KNOWN CHARACTERISTICS OF THE SLAB IN SUBGRADE ARE PRESENTED. THE STRUCTURAL BEHAVIOR OF THE RIGID PAVEMENTS OF THE AASHO ROAD TEST IS STUDIED. IT IS SHOWN THAT THE OVER-ALL RESPONSE OF THE AASHO SUBGRADE TO LOADS IS COMPARABLE TO RESPONSE OF AN IDEAL ISOTROPIC ELASTIC SOLID. WITH PROPER SELECTION OF THE COEFFICIENTS OF SUBGRADE REACTION, THE WINKLER SUBGRADE MODEL (USED IN THE WESTERGAARD THEORY OF RIGID PAVEMENTS) CAN ALSO LEAD TO GOOD PREDICTIONS OF PAVEMENT STRESSES AND DEFLECTIONS. THE COEFFICIENT OF SUBGRADE REACTION FOR THE AASHO PAVEMENT/SUBGRADE SYSTEMS IS A VARIABLE QUALITY, WHICH IS INVERSELY PROPORTIONAL TO THE PAVEMENT SLAB THICHNESS. IT IS DEMONSTRATED THAT THE COMBINED TENSILE STRESS IN PAVEMENT SLABS REPRESENTS THE BEST INDICATOR OF PAVEMENT PERFORMANCE. AN EXPRESSION RELATING THE ULTIMATE NUMBER OF AXLE-LOAD APPLICATIONS TO THE FLEXURAL STRENGTH OF THE PAVEMENT MATERIAL, THE THICKNESS OF THE PAVEMENT SLAB, AND THE MAGNITUDE OF THE AXLE-LOAD IS DESIRED, INDICATING THAT THE PAVEMENT LIFE SHOULD BE PROPORTIONAL TO THE FOURTH POWER OF STRENGTH AND TO THE FIFTH POWER OF SLAB THICKNESS AND INVERSELY PROPORTIONAL TO THE FOURTH POWER OF THE AXLE- LOAD. THIS EXPRESSION OFFERS A RATIONAL BASIS FOR EVALUATION OF A EQUIVALENT NUMBER OF AXLE-LOAD APPLICATIONS FOR RIGID PAVEMENTS SUBJECTED TO MIXED TRAFFIC.