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THE STRUCTURAL DESIGN OF CONCRETE PAVEMENTS: PART 5 - AN EXPERIMENTAL STUDY OF THE WESTERGAARD ANALYSIS OF STRESS CONDITIONS IN CONCRETE PAVEMENT SLABS OF UNIFORM THICKNESS

1943; U.S. Federal Highway Administration; Linguagem: Inglês

0033-3735

L W Teller, E C Sutherland,

Geotechnical Engineering and Analysis

STUDIES WERE CONDUCTED TO BETTER UNDERSTAND THE STRUCTURAL ACTION OF CONCRETE PAVEMENT SLABS. THE OBSERVED STRUCTURAL BEHAVIOR OF PAVEMENT SLABS OF UNIFORM THICKNESS SUPPORTED BY A SUBGRADE AND SUBJECT TO VERTICALLY APPLIED STATIC LOADS WERE COMPARED WITH THE BEHAVIOR INDICATED BY THE WESTERGAARD ANALYSIS. THIS ANALYSIS ASSUMES THAT THE SLAB ACTS AS A HOMOGENEOUS, ISOTROPIC, ELASTIC SOLID IN EQUILIBRIUM AND THAT THE REACTIONS OF THE SOIL ARE VERTICAL ONLY AND ARE PROPORTIONAL TO THE DEFLECTIONS OF THE SLAB. THE RELATIONS BETWEEN APPLIED LOADS AND CRITICAL STRESSES ARE DEVELOPED ON THE BASIS OF ELASTIC THEORY FOR THE THREE CASES OF A WHEEL LOAD APPLIED ON THE SURFACE OF THE SLAB AT A FREE CORNER, AT AN INTERIOR POINT AND AT A FREE EDGE, RESPECTIVELY. THE STUDY OF THE ELASTIC ACTION OF THE SUBGRADE IS REPORTED IN DETAIL. DETERMINATION OF THE MODULUS OF SUBGRADE REACTION MAY BE MADE BY: (1) LOAD-DISPLACEMENT TESTS IN WHICH LOADS ARE APPLIED AT THE CENTER OF RIGID CIRCULAR PLATES OF RELATIVELY SMALL SIZE, THE PRESSURE INTENSITY ON THE SOIL BEING UNIFORM OVER THE ENTIRE AREA OF THE PLATE, (2) LOAD-DISPLACEMENT OR LOAD-DEFLECTION TESTS IN WHICH THE LOAD IS APPLIED AT THE CENTER OF SLIGHTLY FLEXIBLE RECTANGULAR OR CIRCULAR PLATES OF RELATIVELY LARGE DIMENSIONS, AND (3) LOAD-DEFLECTION TESTS ON FULL-SIZE PAVEMENT SLABS IN WHICH THE LOAD-DEFLECTION DATA ARE OBTAINED BY MEASUREMENT AND USED IN THE WESTERGAARD DEFLECTION FORMULAS TO PROVIDE A VALUE FOR THE SOIL STIFFNESS COEFFICIENT OR MODULUS OF SUBGRADE REACTION. THESE TEST METHODS ARE DESCRIBED. THE MODULUS OF SUBGRADE REACTION IS A STIFFNESS COEFFICIENT WHICH EXPRESSES THE RESISTANCE OF THE SOIL STRUCTURE TO DEFORMATION UNDER LOADING POUNDS PER SQUARE INCH OF PRESSURE OF DEFORMATION. THE MAGNITUDE OF THE SEASONAL CHANGE IN SUBGRADE SUPPORT WILL VARY WITH THE CHARACTERISTICS OF THE SOIL MATERIAL AND WITH THE TEMPERATURE AND MOISTURE CHANGES THAT OCCUR. EXPERIMENTS WITH RIGID BEARING PLATES HAVE LED TO THE CONCLUSION THAT USEABLE VALUES FOR THE MODULUS OF SUBGRADE REACTION AS USED IN THE WESTERGAARD EQUATIONS CAN BE OBTAINED BY MEANS OF LOAD-DISPLACEMENT TESTS WITH RIGID BEARING PLATES. THE WESTERGAARD EQUATIONS FOR LOAD-DEFLECTION AND LOAD-STRESS RELATIONS FOR PAVEMENT SLABS OF UNIFORM THICKNESS ARE PRESENTED AND DEVELOPED FOR THE THREE CASES OF LOAD POSITION. STUDIES WERE MADE OF METHODS FOR DETERMINING THE VARIOUS COEFFICIENTS AND OTHER QUANTITIES THAT APPEAR IN THE WESTERGAARD EQUATIONS. THE GENERAL CONCLUSION IS DRAWN THAT THE WESTERGAARD ANALYSIS EXPRESSES QUITE ACCURATELY THE RELATIONS BETWEEN LOAD AND DEFLECTION AND BETWEEN LOAD AND CRITICAL STRESS FOR VARIOUS THICKNESSES OF PAVEMENT AND FOR VARIOUS SIZES OF BEARING AREA PROVIDED THE SLAB IS IN FULL CONTACT WITH THE SUBGRADE.