Base Plate Design
Base plate thickness by the AISC Design Guide 1 cantilever model: the plate cantilevers from the column face under the uniform bearing pressure, and the critical projection decides the thickness.
| Plate length (mm) | Projection (mm) | Thickness (mm) |
|---|---|---|
| 450 | 130 | 31.6 |
| 500 | 130 | 30.0 |
| 550 | 133 | 29.2 |
| 600 | 158 | 33.2 |
| 700 | 208 | 40.5 |
q = Pu/(B·N) · Uniform pressure.
l = max(m, n) · m and n from the column geometry.
tp = √(2·q·l²/(φb·Fy)) · φb = 0.90.
A clear path from inputs to results.
Base plate thickness by the AISC Design Guide 1 cantilever model: the plate cantilevers from the column face under the uniform bearing pressure, and the critical projection decides the thickness.
How to use
- Set axial load pu (kn).
- Set plate width b (mm).
- Set plate length n (mm).
- Set column depth d (mm).
- Read the headline metrics, then check the table for the detail.
The formula
Reference: AISC DG1 cantilever model for a concentrically loaded base plate.
Worked example
At the default inputs
- Axial load Pu (kN): 1500; Plate width B (mm): 500; Plate length N (mm): 550; Column depth d (mm): 300; Column flange bf (mm): 300; Concrete f'c (MPa): 30; Plate Fy (MPa): 250
- 1
Required thickness: 29.2 mm · Bearing pressure: 5.45 MPa · Critical projection: 133 mm · Bearing check: OK
Required thickness: 29.2 mm · Bearing pressure: 5.45 MPa · Critical projection: 133 mm
Interpreting the result
A 1500 kN column on a 500×550 plate needs 29.2 mm of plate.
Assumptions & limitations
- Concentric axial load only.
- Plate is rigid relative to the concrete.
Frequently asked questions
Why does a longer plate not always help?
It lowers the bearing pressure but lengthens the cantilever, and the thickness goes with the projection squared.
What about uplift or moment?
Those need the DG1 anchor and eccentricity provisions, not this check.
Methodology last reviewed 2026-10-22. Results are informational and not financial or engineering advice — see our disclaimer.