ANALYSIS OF CONCRETE SLABS ON GROUND SUBJECTED TO WARPING AND MOVING LOADS

Abstract

A THEORY HAS BEEN DEVELOPED WHEREBY STRESSES AND DEFLECTIONS COULD BE CALCULATED FOR A SERIES OF RECTANGULAR SLABS LYING ON A VISCOELASTIC FOUNDATION AND SUBJECTED TO A MOVING LOAD. THE STRESSES AND DEFLECTIONS ARE CAUSED BY THE WEIGHT OF THE SLAB, THE MOVING CONCENTRATED LOAD, AND THE LINEAR TEMPERATURE (OR MOISTURE) VARIATIONS THAT CAUSE SUFFICIENT WARPING SO THAT THE SLAB IS ONLY PARTIALLY SUPPORTED BY ITS FOUNDATION. THE SUPPORT CONDITIONS WERE SIMULATED BY A KELVIN VISCO-ELASTIC MODEL, AND ZONES (WHICH DEPENDED ON THE VALUE OF SUB-GRADE REACTION) WERE SET UP SO THAT THE SOLUTIONS TO THE GOVERNING DIFFERENTIAL EQUATIONS COULD BE REDUCED TO A SET OF SIMULTANEOUS ALGEBRAIC EQUATIONS. THE EQUATIONS WERE SOLVED WITH THE AID OF AN IBM 7090 DIGITAL COMPUTER USING A FORTRAN SOURCE PROGRAM. IT WAS FOUND THAT WHEN PARTIAL SUPPORT CAUSED BY WARPING EXISTS, THE TENSILE STRESS IN THE SLAB CAN INCREASE WITH INCREASING VELOCITY OF LOAD. MOREOVER, THE MAXIMUM DEFLECTION (DOWNWARD) NEED NOT OCCUR WHEN THE VELOCITY OF THE LOAD IS EQUAL TO ZERO. THE REDUCTION IN SUBGRADE SUPPORT OVER A NARROW REGION (8 FT. OR LESS) LEADS TO DEFLECTIONS AND STRESSES THAT ARE HIGHER THAN THOSE CALCULATED USING THE INITIAL VALUE OF SUBGRADE REACTION. THIS IS PARTICULARLY EVIDENT WHEN THE LOAD IS OVER THE REGION OF REDUCED SUBGRADE REACTION. /AUTHOR/