STRESSES AND DISPLACEMENTS IN AN ELASTIC MASS UNDER ASSUMED AND MEASURED TIRE PRESSURES

THE PURPOSE IS TO COMPARE THE DIFFERENCES IN MAGNITUDE OF VERTICAL STRESSES AND DISPLACEMENTS IN THE SUPPORTING MEDIUM ARRIVED AT BY COMPUTATIONS BASED ON ASSUMED AND MEASURED TIRE PRESSURES. USING THE ELASTIC THEORY, COMPUTATIONS WERE MADE FOR VARIOUS POINTS ALONG THE VERTICAL AXIS UNDER THE HIGHER EDGE PRESSURE IN CASES OF LOW-PRESSURE TIRES COMPUTATIONS FOR THE UNIFORM PRESSURE DISTRIBUTIONS WERE BASED ON CIRCULAR AND RECTANGULAR CONTACT AREAS. ASSUMED PARABOLIC PRESSURE DISTRIBUTIONS OVER CIRCULAR CONTACT AREAS WERE STUDIED. TEST TIRES CONSISTED OF AN 11.00-20 BUFF SMOOTH TIRE AND A 12-22.5 TREADED TIRE. ANALYSIS WAS MADE WITH TIRES OF 12-PLY RATING (COMMONLY USED FOR MILITARY LAND VEHICLES). MEASUREMENTS WERE MADE IN SOFT SOILS (SANDS AND CLAYS) WITH A TOWED (ABOUT 1 MPH) SMOOTH TIRE AND ON A HARD SURFACE UNDER STATIC AND TOWD CONDITIONS. AT ONE TEST LOAD, THE MEASUREMENTS WERE MADE AT 3 DIFFERENT TIRE-INFLACTION PRESSURES. EACH SOFT SOIL WAS TESTED AT DIFFERENT LEVELS OF STRENGTH. SINCE COMPUTED RESULTS FOR UNIFORMLY DISTRIBUTED PRESSURES ARE NEARLY IDENTICAL FOR CIRCULAR AND RECTANGULAR AREAS, ONLY THE RESULTS FOR UNIFORM RECTANGULAR LOADS ARE PRESENTED. BECAUSE RELATIVELY HIGH PRESSURES WERE MEASURED NEAR THE EDGE OF THE CONTACT AREA, COMPUTATIONS WERE MADE ALONG THE VERTICAL AXIS UNDER HIGH EDGE PRESSURE, AND THE RESULTS WERE COMPARED WITH THOSE ALONG THE VERTICAL AXIS UNDER THE CENTER OF THE UNIFORM PRESSURE DISTRIBUTION, WHERE MAXIMUM STRESS AND DISPLACEMENT WOULD OCCUR. THE RESULTS FOR A LOW PRESSURE TIRE LOADED TO 3,000 LBS. AND TOWED OVER SAND AT THREE DIFFERENT STRENGTHS ARE GIVEN. SAND CONDITIONS RANGED FROM LOOSE TO DENSE. IT IS CONCLUDED THAT FOR HIGH-PRESSURE TIRES ON HARD SURFACE AND SANDS, THE STRESSES IN THE FORMER CASE AND STRESSES AND DISPLACEMENTS IN THE LATTER CASE COMPUTED FROM MEASURED PRESSURE DISTRIBUTION ARE MUCH HIGHER THAN THOSE COMPUTED FROM AN ASSUMED UNIFORM PRESSURE DISTRIBUTION. THE ASSUMPTION OF UNIFORM PRESSURE DISTRIBUTION ON CLAY IS REASONABLE IF THE TIRE-INFLATION PRESSURE IS LOW. THE ASSUMPTION OF PAROBOLIC PRESSURE DISTRIBUTION IS MORE REALISTIC THAN THAT OF A UNIFORM ONE FOR HIGH PRESSURE TIRES ON SAND AND FOR LOW PRESSURE TIRES WITH LIGHT LOAD ON LOOSE SAND.

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• Supplemental Notes:
  • No 345, pp 58-61, 1 FIG, 3 REF
• Authors:
  • Chou, Y T
• Publication Date: 1971

Media Info

• Serial:
  • Highway Research Record
  • Publisher: Highway Research Board

Subject/Index Terms

• TRT Terms: Calculation; Clay; Dislocation (Geology); Parabolas; Paving; Pressure; Sand; Soils; Standardization; Stresses; Tires
• Uncontrolled Terms: Computation; High pressure; Pressure distribution
• Old TRIS Terms: Hard surfacing; Low pressure
• Subject Areas: Geotechnology; Highways; Pavements; Vehicles and Equipment;

Filing Info

• Accession Number: 00205935
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Sep 13 1971 12:00AM