FLEXIBLE PAVEMENT DEFLECTION: THREE STUDIES

IN 1963, NEW YORK STATE INITIATED A BENKELMAN BEAM DEFLECTION INVESTIGATION OF ITS FLEXIBLE PAVEMENTS TO ESTABLISH AN OVERALL PICTURE OF THEIR DEFLECTION PROPERTIES. PAVEMENTS WERE SELECTED WHICH LENT THEMSELVES TO THREE BASICALLY DIFFERENT STUDIES. THE FIRST WAS TO DETERMINE THE MAGNITUDE AND VARIATION OF PAVEMENT DEFLECTIONS, IN RELATION TO SPRING AND FALL CHANGES IN REPRESENTATIVE CLIMATE ZONES THROUGHOUT THE STATE. THE SECOND WAS A DETAILED INVESTIGATION OF RATE OF CHANGE OF PAVEMENT DEFLECTIONS DURING WINTER AND SPRING THAW PERIODS, AND INVOLVED DAILY DEFLECTION MEASUREMENTS. THE THIRD WAS TO INVESTIGATE DEFLECTIONS ON SEVERAL COURSES OF A SINGLE FLEXIBLE PAVEMENT DURING ITS CONSTRUCTION, AND FOR A BRIEF PERIOD IN SERVICE. MANY PREVIOUSLY ESTABLISHED PRINCIPLES CONCERNING FLEXIBLE PAVEMENT DEFLECTIONS WERE CONFIRMED. AMONG THESE WERE THAT SPRING DEFLECTIONS ARE GREATER THAN FALL DEFLECTIONS, THAT DEFLECTIONS INCREASE WITH DECREASING PAVEMENT THICKNESS, AND THAT DEFLECTIONS INCREASE RAPIDLY DURING THE SPRING THAW. HOWEVER, THE DATA DID INDICATE THAT ONE PREVIOUS ASSUMPTION SHOULD BE QUALIFIED. OUTER WHEEL- PATH DEFLECTIONS ARE NOT ALWAYS GREATER THAN THOSE IN THE INNER WHEELPATH. FOR THICKER, NEWER PAVEMENTS TEST DATA SHOWED LITTLE OR NO DIFFERENCE. HOWEVER, ON THINNER, OLDER PAVEMENTS THE OUTER WHEELPATH DEFLECTIONS WERE GREATER. ANALYSIS ALSO DEALT WITH CORRELATIONS BETWEEN SPRING AND FALL READINGS, CORRELATIONS BETWEEN READINGS, ON UNCRACKED AND CRACKED PAVEMENT SECTIONS, DAY-TO-DAY DEFLECTION CHANGES DURING A WINTER AND A SPRING THAW, AND DETERMINATION OF WHEN DEFLECTIONS INCREASED DURING THE WINTER AND SPRING IN RELATION TO WEATHER CONDITIONS. /AUTHOR/