> ## Documentation Index
> Fetch the complete documentation index at: https://calcs.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# HSS Steel Base Plate
> Design HSS column base plates for compression, uplift and brace loading, with anchor rod, concrete breakout and weld checks.
**Where you can use this:** [Atlas Tube HSS Connections Hub](https://connectionshub.atlastube.com/login/organisations?src=CALCSDOCS) only
**Status:** Beta · **Region:** US · **Design codes:** AISC 360-22, AISC Design Guide 1, ACI 318-19
## What this calculator does
Designs and checks an HSS column base plate and its anchorage. The calculator now covers five things it could not do before, which together take it from a compression-only, four-rod tool to one that handles real base plates including brace loading.
## Video walkthrough
Atlas Tube engineer Jason McNeil works a complete base plate calculation for a rectangular HSS column (an HSS 18x6x1/2 example), covering plate and pedestal dimensions, anchor rod properties and embedment depth, grout and cracked-concrete conditions, factored loads, the concrete pullout, breakout and pryout checks, and the force transfer considerations that differ between rectangular and round HSS columns.
## What is new
### Anchor layouts beyond 2 x 2
Enter the number of rods along each axis and the calculator builds the pattern, then recalculates spacing, edge distances and the concrete breakout areas for the group. Previously any layout with more than four rods had to be done by hand.
### Concrete pier depth as an input
The confinement area A2 is now derived from the pier rather than typed in, which removes a step that is easy to get wrong and easy to leave conservative by default. It also means the shallow-member thickness factor of ACI 318-19 Cl. 17.7.2.6 finally has a value in the shear breakout check.
### Net uplift
Load combinations that lift the column are no longer rejected. The calculator:
* Checks the rods for steel tension, pullout and breakout
* Reduces the rod tensile strength for coexisting shear per AISC 360-22 Cl. J3.8
* Finds the load in the governing rod by elastic group analysis, AISC Design Guide 1 Eq. 4-67
* Sizes the plate for uplift bending using the 45 degree effective width from Design Guide 1 Example 4.7-3
### Column-to-plate weld check
Combined tension, shear and moment demand per Design Guide 1 Cl. 4.5.2, checked against the directional method of AISC 360-22 Cl. J2.4. The weld runs along the four HSS workable flats.
### Shear distribution between anchor rows
Where the rods are welded to the plate, shear can be resisted by the rear row alone or shared with the front row, following the Case 1, 2 and 3 treatment in ACI 318-19 Fig. R17.7.2.1b.
## Inputting key properties
1. **Select the HSS column section and grade.**
2. **Enter the base plate dimensions and grade.**
3. **Enter the concrete pier dimensions including depth**, the concrete strength, and whether the concrete is cracked or uncracked.
4. **Set the grout condition.**
5. **Enter the anchor rod layout:** number of rods along each axis, diameter, grade, embedment depth, and whether rods are welded to the plate. The diagram redraws as you change the count and direction.
6. **Set the shear transfer case** where rods are welded.
7. **Enter the weld size** for the column-to-plate weld.
The calculator only shows the checks the load case needs. Switch a load combination from uplift to compression and the tension-side checks disappear, because they no longer apply. If you expected to see a pullout or breakout check and it is not there, look at your load case first.
## Applying loads
Axial compression, axial tension (uplift), shear and moment, including brace loading into the base.
## Reviewing the calculations
| Limit state | Reference |
| ------------------------------------------------------ | ----------------------------------------- |
| Concrete bearing | AISC 360-22 J8, ACI 318-19 |
| Base plate bending, compression side | AISC Design Guide 1 |
| Base plate bending, uplift, 45 degree effective width | AISC Design Guide 1 Example 4.7-3 |
| Anchor rod steel tension | ACI 318-19 Ch. 17 |
| Anchor rod pullout | ACI 318-19 Ch. 17 |
| Concrete breakout in tension | ACI 318-19 Ch. 17 |
| Concrete pryout | ACI 318-19 Ch. 17 |
| Concrete breakout in shear, with shallow-member factor | ACI 318-19 Cl. 17.7.2.6 |
| Combined tension and shear in rods | AISC 360-22 Cl. J3.8 |
| Governing rod load by elastic group analysis | AISC DG 1 Eq. 4-67 |
| Column-to-plate weld, combined demand | AISC DG 1 Cl. 4.5.2, AISC 360-22 Cl. J2.4 |
Plan and elevation diagrams redraw from the geometry, so they follow any layout and show the pier depth.
## Change in results
This release corrects the concrete breakout strength parallel to a free edge, which was previously being applied twice. Designs governed by anchor shear breakout will see utilisation rise. The new value is the correct one, so re-check any base plate designed before this update where shear breakout governed.
## Related
* [Column bracing to shear connection linking](/docs/connections_hub/workflows/column_bracing_linking)
**Where you can use this:** [Atlas Tube HSS Connections Hub](https://connectionshub.atlastube.com/login/organisations?src=CALCSDOCS) only
**Status:** Beta · **Region:** US · **Design codes:** AISC 360-22, AISC Design Guide 1, ACI 318-19