Description

This verification example utilizes Tekla Tedds to check a slab on ground with a vehicle wheel loading assigned a specific design index utilizing the Corps of Engineer’s (COE) method. This example is based on Design Example A3.2 of the ACI 360R-10 Guide to Design of Slabs-on-Ground (page 63). Comparisons and contrasts are tabularized and discussed regarding the results from Tedds and the ACI Design Example. The Tedds file used in this example is provided in the Tedds “Select Calculation” window, under Verification Examples.

Problem statement

Determine the slab thickness due to loading a vehicle wheel loading in design index Category IV.

References

ACI 360R-10 Guide to Design of Slabs-on-Ground

Example information

Loading: Design Index Category IV

Capacity = 16,000 lb

Design axle load = 36,000 lb

Number of tires = 6

Type of tire: Pneumatic

Tire contact area = 100 in²

Effect contact pressure = 90 psi

Tire width = 9”

Wheel spacing = 13” / 58” / 13”

Aisle Width = 144”

Spacing between dual wheel tires = 4”

Modulus of elasticity, E = 4,000 ksi

Concrete compressive strength, f’c = 5,000 psi (determined by f’c = (E/57,000)²)

Modulus of rupture = 615 psi

Subgrade modulus, k = 100 lb/in³

Notes

• Both Tedds and the ACI design example utilize the COE design chart found in ACI 360R-10 (Figure A3.1)

• The thickness is based on limiting the tension on the bottom of the concrete slab at an interior joint of the slab. The procedure uses an impact factor of 25% and a factor of safety of approximately 2. The joint transfer coefficient has been taken as 0.75 for the design chart in Figure A3.1 of ACI 360R-10.

Conclusion

Upon reviewing the results above, the determination of slab on ground thickness due to vehicle wheel loading following the COE method by Tekla Tedds matches ACI 360R-10 design example A3.2. Differences between Tedds and the example can be attributed to rounding of values in the ACI design example.