Steel Base Plate (LRFD, ACI 318-19 / AISC 360-16)
Run the calcBase plate design receives column axial load directly, change the column load and the plate thickness and anchor check update automatically. Designs steel column base plates and anchor rods to ACI 318-19 and AISC 360-16 under LRFD, checking bearing, plate bending, and all anchor limit states.
This calculator uses an earlier code edition (ACI 318-19, AISC 360-16, AISC Steel Design Guide 1 (2006): Base Plate and Anchor Rod Design - 2nd Edition). It stays available for existing projects. For new designs, check the Calculator Library for the current edition.
Method & scope
Calculation method
The Steel Base Plate (LRFD, ACI 318-19 / AISC 360-16) calculator applies AISC Steel Design Guide 1 (2nd Edition) for plate geometry and bending, with anchor limit states updated to ACI 318-19 Chapter 17. Load combinations follow ASCE 7-16.Load combinations
Unfactored dead, live, wind, and seismic loads are combined into governing ASCE 7-16 LRFD combinations. The critical combination for each check is identified automatically, compressive axial load governs bearing, while the combination producing maximum moment and minimum axial load governs anchor tension.Concrete bearing capacity (AISC DG1 Cl 3.1)
The factored concrete bearing strength: phi × P_p = phi_c × 0.85 × f’c × A_1 × sqrt(A_2/A_1) ≤ 1.7 × phi_c × f’c × A_1 Utilization = P_u / phi × P_p ≤ 1.0Plate bending (AISC DG1 Cl 3.3, 3.4)
The plate is checked at the bearing interface and tension interface in both X and Y axes. The critical plate moment demand M_u,pl (kip-in/in of plate width) is the maximum of the cantilever bending from bearing pressure over projections m and n. Required plate thickness from bending: t_min = sqrt(4 × M_u,pl / (phi_p × F_y)) Utilization = M_u,pl / phi × M_n ≤ 1.0Anchor rod tensile limit states (ACI 318-19 Cl 17.6)
Five tensile limit states are checked for the anchor group:- Steel tensile capacity (Cl 17.6.1): phi_t × N_sa = phi_t × A_se × f_uta per rod
- Concrete breakout in tension (Cl 17.6.2): CCD method with projected area A_Nc, modification factors for edge distance, eccentricity, and cracking
- Pullout (Cl 17.6.3): phi × 8 × A_brg × f’c for headed anchors
- Side-face blowout (Cl 17.6.4): applies when h_ef ≥ 2.5 × c_a1
- Group effects: anchor spacing and edge proximity reduction factors
Anchor rod shear limit states (ACI 318-19 Cl 17.7)
Three shear limit states are checked in each principal axis:- Steel shear capacity (Cl 17.7.1): phi_v × V_sa = phi_v × 0.6 × A_se × f_uta
- Concrete pryout (Cl 17.7.3): governs for short embedment depths
- Concrete shear breakout (Cl 17.7.2): projected area method with edge distance factors
Frictional shear capacity (ACI 318-19 Cl 22.9)
Base friction under compressive axial load supplements anchor shear capacity. Friction coefficient mu = 0.55 for steel on grout and 0.70 for steel on concrete.Seismic provisions
When a seismic design category (C through F) is selected, the calculator applies the additional ACI 318-19 Chapter 17 requirements, including the seismic strength reduction factor and the requirement that anchor steel controls over concrete failure modes where applicable.How to use it
1
Open the calculator
Open it from Run calc in the About this calculator panel above.
2
Enter your inputs
Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See Checks, References, Conditions and Assumptions.
3
Review the results and export
Check the utilization of each governing check in the summary, then export a PDF report. See Views and Export.
Common questions
What codes and method does this calculator use?
What codes and method does this calculator use?
The calculator follows AISC Steel Design Guide 1, 2nd Edition (2006) for base plate sizing and plate bending, with anchor rod capacities per ACI 318-19 Chapter 17. Load combinations are generated per ASCE 7-16 Chapter 2.
What are the key inputs?
What are the key inputs?
Inputs include the column section, base plate dimensions and material grade, anchor rod diameter, grade, and embedment depth, concrete edge distances and spacings, concrete compressive strength, and unfactored column loads (axial, biaxial moments, and shear in both directions). The seismic design category can be toggled to apply ACI 318-19 seismic provisions.
What limit states does it check?
What limit states does it check?
The calculator checks: concrete bearing strength, plate bending capacity at the bearing and tension interfaces in both axes, anchor rod steel tensile capacity (ACI 318-19 Cl 17.6.1), pullout (Cl 17.6.3), concrete breakout in tension (Cl 17.6.2), side-face blowout (Cl 17.6.4), anchor rod steel shear capacity (Cl 17.7.1), concrete pryout (Cl 17.7.3), concrete shear breakout in both axes (Cl 17.7.2), and frictional shear capacity (Cl 22.9).
Can it handle combined moment and axial loading?
Can it handle combined moment and axial loading?
Yes. The calculator resolves biaxial moments M_ux and M_uy with the factored axial load P_u to determine the bearing pressure distribution across the plate. It applies the appropriate small-moment (full contact) or large-moment (partial contact with anchor tension) approach from AISC Design Guide 1 for both plate bending and anchor demands.
What concrete strengths and anchor rod specifications are supported?
What concrete strengths and anchor rod specifications are supported?
Any concrete compressive strength f’c can be specified. Anchor rods are defined by diameter, embedment depth, and material grade (ASTM F1554 or equivalent). When seismic provisions apply, the calculator incorporates the additional ACI 318-19 Chapter 17 requirements for anchors in seismic design categories C through F.
Can this calculator receive column axial load directly from a column calculator?
Can this calculator receive column axial load directly from a column calculator?
Yes, the base plate calculation receives axial and shear loads from the column calculation above. When the column size or loading changes, the base plate demand updates automatically. This load-linking removes the need to manually transfer forces between calculations.
Next steps
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