Verification Example - Slab on Ground - Post Loading (PCA method)

Tekla Tedds
Modifié: 17 déc 2024
2024
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Verification Example - Slab on Ground - Post Loading (PCA method)

Description

This verification example utilizes Tekla Tedds to check a slab on ground with a grid of post loads such as from rack storage supports. This example is based on Design Example A1.3 of the ACI 360R-10 Guide to Design of Slabs-on-Ground (page 59). 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 by a grid of posts.

References

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

Concrete Floors on Ground (2001) by PCA

Example information

The post configuration and loads can be seen in Figure A1.4 of ACI 360R-10.

 

Loading: Post Load = 15.5 kips

Plate contact area for each post = 36 in2

Long spacing, y = 100 in.

Short spacing, x = 40 in.

Concrete compressive strength, f’c = 4,000 psi

Modulus of rupture = 9√f’c = 570 psi

Subgrade modulus, k = 100 lb/in3

Factor of safety = 1.4 (determined from ACI 360R-10 Table 5.2)

Notes

  • 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)

  • Both Tedds and the ACI design example utilize the PCA design charts found in ACI 360R-10 (Figures A1.5, A1.6, and A1.7)

  • 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 A1.3
Component Tedds Result ACI Design Example 1.3 % Difference
Allowable stress 406.6 psi 407 psi 0.1%
Stress per 1,000 lb of post load 26.2 26.3 (value of 26 was used) 0.4%
Required slab thickness 8.08” 8.25” 2.0%

Conclusion

Upon reviewing the results above, the determination of slab on ground thickness due to post loads by Tekla Tedds matches ACI 360R-10 design example A1.3. Differences between Tedds and the example can be attributed to rounding of values in the ACI design example.

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