Steel Base Plate (LRFD, ACI 318-14 / 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 318-14 and AISC 360-16 under LRFD, checking bearing, plate bending, and all anchor limit states.
This calculator uses an earlier code edition (ACI 318-14, 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) calculator follows AISC Steel Design Guide 1 (2nd Edition, 2006) for plate sizing and plate bending, and ACI 318-14 Chapter 17 for all anchor rod limit states. Factored load combinations are generated per ASCE 7-16.Load combinations
Dead, live, wind, and seismic loads are entered as unfactored components. The calculator generates all governing ASCE 7-16 LRFD combinations (1.2D + 1.6L etc.) and identifies the critical factored axial load P_u, biaxial moments M_ux and M_uy, and shear demands V_ux and V_uy for each subsequent check.Concrete bearing capacity (AISC DG1 Cl 3.1)
The factored concrete bearing strength under the plate is: phi × P_p = phi_c × 0.85 × f’c × A_1 × sqrt(A_2/A_1) where A_1 is the base plate area and A_2 is the supporting surface area. The geometry factor sqrt(A_2/A_1) is limited to 2.0 per ACI 318-14. Utilization = P_u / phi × P_p ≤ 1.0Plate bending, bearing interface (AISC DG1 Cl 3.3, 3.4)
When the plate is in the small-moment regime (full contact), the plate bending demand at the bearing interface is calculated from the upward bearing pressure over the cantilever projections m and n beyond the column flange and web. The critical plate moment demand M_u,pl (kip-in/in) is compared to the plate bending capacity: phi × M_n = phi_p × F_y × t^2 / 4 Utilization = M_u,pl / phi × M_n ≤ 1.0 The minimum required plate thickness t_min is reported from this check.Plate bending, tension interface (AISC DG1 Cl 3.3, 3.4)
For large-moment conditions where anchor rods carry tension, the plate is also checked for bending at the tension interface. The anchor rod tensile force creates an upward pull on the plate, and the resulting plate moment is evaluated against phi × M_n.Anchor rod tensile capacity (ACI 318-14 Cl 17.4)
The calculator checks five tensile limit states for the anchor rod group:- Steel tensile strength: phi_t × A_se × f_uta
- Concrete breakout (CCD method): based on projected cone area A_Nc relative to basic area A_Nco
- Pullout capacity: phi × 8 × A_brg × f’c per rod
- Side-face blowout: applicable when embedment depth is large relative to edge distance
- Group effects: interaction factors for closely spaced anchors
Anchor rod shear capacity (ACI 318-14 Cl 17.5)
Shear demand is checked against:- Steel shear capacity: phi_v × 0.6 × A_se × f_uta
- Concrete pryout: phi × k_cp × N_cbg (governs for shallow embedments)
- Concrete shear breakout in both X and Y axes using the projected area method
Frictional shear capacity (ACI 318-14 Cl 22.9)
The base plate can transfer shear through friction between the plate and the grout or concrete. The friction capacity phi × mu × P_u is added where applicable to supplement anchor shear resistance.Minimum required plate thickness
The governing minimum plate thickness t_min is reported as the maximum value from the bearing interface check and the tension interface check across both axes.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 318-14 Chapter 17. Load combinations are generated per ASCE 7-16 Chapter 2 and ACI 318-14 Chapter 13.
What are the key inputs?
What are the key inputs?
Inputs include column section properties, base plate dimensions (length, width, thickness) and material grade, anchor rod diameter, grade, embedment depth, edge distances and spacing, concrete compressive strength, and applied column axial load and biaxial moments. Dead, live, wind, and seismic loads are entered separately for automatic LRFD combination generation.
What limit states does it check?
What limit states does it check?
The calculator checks: concrete bearing strength (factored bearing vs phi × P_p), plate bending capacity at both the bearing and tension interfaces in both X and Y axes (phi × M_n vs M_u,pl), anchor rod steel tensile and shear capacity (ACI 318-14 Cl 17.4 and 17.5), concrete breakout and pullout in tension (Cl 17.4), concrete pryout and breakout in shear (Cl 17.5), side-face blowout (Cl 17.4.4), and frictional shear capacity (Cl 22.9).
Can it handle moment and axial combined loading on the base plate?
Can it handle moment and axial combined loading on the base plate?
Yes. Biaxial moments (M_ux and M_uy) are resolved at the base plate together with the axial load. The calculator determines the critical bearing pressure distribution under the plate, identifies whether the plate is in a small-moment (full bearing) or large-moment (partial bearing with anchor tension) regime, and applies the appropriate AISC Design Guide 1 approach for plate thickness and anchor demand.
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 input. Anchor rods are specified by diameter, material grade (ASTM F1554 or equivalent), and embedment depth. Seismic provisions under ACI 318-14 Chapter 17 for anchor design in seismic design categories can be toggled.
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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