Verification Example - Slab on Ground - Single-Axle Loading (PCA method)
Description
This verification example utilizes Tekla Tedds to check a slab on ground for single-axle loading with single wheels at each end. This example is based on Design Example A1.2 of the ACI 360R-10 Guide to Design of Slabs-on-Ground (page 58). 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 single-axle loading with single wheels at each end.
References
ACI 360R-10 Guide to Design of Slabs-on-Ground
Concrete Floors on Ground (2001) by PCA
Example information
Loading: Axle Load = 22.4 kips
Effective contact area of one wheel = 25 in2
Wheel spacing = 40 in.
Subgrade modulus, k = 200 lb/in3
Concrete compressive strength, f’c = 4,000 psi
Modulus of rupture = 9√f’c = 570 psi
Factor of safety = 1.7 (determined from ACI 360R-10 Table 5.2)
Notes
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The procedure to determine slab on ground thickness for post loads utilizes design charts published by Portland Cement Association (PCA) in Concrete Floors on Ground (2001)
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Both Tedds and the ACI design example utilize the PCA design charts found in ACI 360R-10 (Figures A1.1 and A1.2)
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The thickness is based on limiting the tension on the bottom of the concrete slab.
Comparison of Results between Tedds and ACI 360R-10 Design Example A1.2 | |||
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Component | Tedds Result | ACI Design Example 1.2 | % Difference |
Allowable stress | 334.8 psi | 335 psi | 0.1% |
Stress per 1,000 lb of axle load | 14.9 | 14.96 (value of 15 was used) | 0.4% |
Required slab thickness | 7.56” | 7.75” | 2.5% |
Conclusion
Upon reviewing the results above, the determination of slab on ground thickness due to single-axle wheel loads by Tekla Tedds matches ACI 360R-10 design example A1.2. Differences between Tedds and the example can be attributed to rounding of values in the ACI design example.