Let us assume a square gravity foundation block.
The Safety Factor Against Sliding ( FS_SL ) is then calculated:
Notes and next steps (brief)
Driving force ( H_d = 1.5 \times 75 = 112.5 , kN ) ( FOS_slide = 1030 / 112.5 = 9.2 \gg 1.5 ) → OK. tower crane foundation design calculation example link
The restoring moment caused by the self-weight of the concrete and crane must safely exceed the overturning moment.
We check if the eccentricity falls within the middle third of the footing base to prevent uplift (where the footing lifts off the soil):
The design process must consider both the maximum pressure ( Pmax ) and the average pressure ( Pavg ) applied to the soil. Let us assume a square gravity foundation block
): The wind forces acting on the crane structure and the hooked load. Overturning Moment (
Calculate bottom steel bars to resist bending moments.
: Verify the foundation’s resistance to overturning and sliding. A standard safety factor (often ≥1.5is greater than or equal to 1.5 We check if the eccentricity falls within the
Below is a concise, worked example showing the typical steps and calculations used to size a shallow spread foundation for a small tower crane. This is a simplified illustrative example only — always verify with a licensed structural/geotechnical engineer and local codes before construction.
$$2.06 \text ksf < 3.0 \text ksf (SBC)$$ Pass. The soil can safely support this foundation.
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