A MODEL STUDY OF SLAB ACTION IN CONCRETE PAVEMENTS

AN ATTEMPT HAS BEEN MADE TO STUDY THE EFFECT OF WHEEL LOADS UPON CONCRETE SLABS BY THE USE OF MODELS. A SLAB OF DIMENSIONS 33 IN. BY 15FT. BY 2 IN. WAS CAST IN A LABORATORY UPON A SOIL SUBGRADE. SR-4 ELECTRIC STRAIN GAGES WERE CEMENTED TO THE CONCRETE AND DEFLECTION DIALS WERE SUPPORTED AT STRATEGIC LOCATIONS. SHOES REPRESENTING WHEEL CONTACT AREAS WERE CONSTRUCTED AND LOADS APPLIED THROUGH THESE AREAS IN A VARIETY OF ARRANGEMENTS. RESULTS OF THE TEST SHOW THAT A GIVEN LOAD ON AN AXLE WITH FOUR OR SIX WHEELS WILL CAUSE ALMOST AS MUCH STRAIN IN THE CONCRETE AS ONE WITH ONLY TWO WHEELS. HOWEVER, IF THE LOAD IS DISTRIBUTED OVER TWO AXLES THERE IS AN OPTIMUM AXLE SPACING SUCH THAT MORE THAN TWICE THE SINGLE AXLE LOAD MAY BE SUPPORTED BY THE SYSTEM WITHOUT PRODUCING A STRAIN GREATER THAN THAT CAUSED BY A SINGLE AXLE. LIKEWISE FOR THREE AXLES THE SYSTEM MAY CARRY MORE THAN THREE TIMES THE SINGLE AXLE LOAD WITHOUT INCREASING THE STRAIN, PROVIDING THE AXLES ARE PROPERLY SPACED. /AUTHOR/