KEVOS® MAKEOS · Engineering
Tapered Pad Footing Check (Prismoidal Volume, Self-Weight, Bearing Pressure, Concrete Order)
For a column pad footing with a tapered top, how much concrete does it take, what does it weigh, and is the bearing pressure under it within the ground’s allowable pressure?
Check of a square or rectangular pad footing with a straight base block and a tapered (frustum) top: the volume of the taper by the prismoidal formula (as the prismoidal volume tool) plus the base block, the self-weight, the bearing pressure under the base from the column load and self-weight against your allowable ground pressure, the base area needed, and the concrete to order with a waste allowance.
Open the calculatorRuns in your browser. No account needed.
How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Base length | mm | Length of the footing base. |
| Base width | mm | Width of the footing base. |
| Depth of the straight base block | mm | Depth of the vertical-sided block at the bottom. |
| Top length (at the column) | mm | Length of the flat top where the column or plinth sits. |
| Top width (at the column) | mm | Width of the flat top. |
| Height of the tapered part | mm | Height of the sloping part above the base block. |
| Loads and ground | ||
| Column load on the footing | kN | Load the column brings down onto the footing. |
| Concrete density | kg/m³ | Density of the concrete (about 2400 for reinforced concrete). |
| Allowable bearing pressure of the ground | kPa | Allowable bearing pressure of the ground, from site investigation. |
| Waste allowance on the order | % | Extra concrete to order for spillage and over-excavation. |
Method and formulas
- Taper volume V = h (A₁ + 4A_m + A₂) ÷ 6 with the middle section from the averaged sides (as the prismoidal volume tool).
- Block volume = a₁ b₁ h_b; self-weight = volume × density × g.
- Bearing pressure = (P + self-weight) ÷ (a₁ b₁); base area needed = (P + self-weight) ÷ allowable pressure.
- Example: 0.63733 m³ of concrete weighing 15 kN; the ground carries 218.75 kPa.
Limitations
- Concentric vertical load; moments or horizontal loads make the pressure uneven.
- Reinforcement, punching shear and settlement need a structural design.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Size a pad for a column or machine leg
- Order concrete for tapered footings
- Check a footing for a heavier load
Who it is for
- Site engineers
- Plant engineers
- Builders
What you get
- Taper, block and total volume
- Self-weight and bearing pressure
- Base area needed and concrete to order
Interpreting the result
- Tapering the top saves concrete with little effect on the bearing pressure, which depends on the base area.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 66. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
