FrameAI/ AISC/ Connections/ Column Baseplate
AISC 360-22 §J8 · AISC DG-1 (2nd Ed.) · ACI 318-22 §22.8 · LRFD · Imperial

Column Baseplate
Moment Connection

Design guide for column baseplates under combined axial + moment + shear — cantilever model per DG-1 Eq. 3.3.1–3.3.4, anchor tension per §J8, concrete bearing per ACI 318-22 §22.8.3.2.

When to use this
Use this baseplate moment connection when a steel column bears on a concrete foundation and must resist a factored moment in addition to axial compression or tension — portal frame bases, eccentrically loaded columns, braced frame nodes with moment diagrams at the base, or crane runway columns. For pinned base conditions (shear only, zero moment), use the shear-baseplate check only. For anchor rods in tension without a baseplate (steel-to-concrete直接的连接), use the embedded anchor design per §IBC Chapter 18.
Configuration — plan + isometric schematic
R1 R2 R3 R4 N = 20 in B = 20 in Plan view CJP or fillet §J2.4/AWS D1.1 W14×90 d = 14.02 in A992 Gr.50 20×20×1 in A572 Gr.50 F1554-Gr36 1 in Ø 4× anchor rods Isometric Baseplate Anchor rod Weld
Worked Example — W14×90 · 20×20×1 in plate · F1554-Gr36 1 in anchors · 4 ksi concrete · 400 kip-ft
Column
W14×90
d = 14.02 in   bf = 14.52 in
tf = 0.710 in   tw = 0.440 in
Fy = 50 ksi · A992 Gr.50
Base Plate
A572 Gr.50
N = 20 in   B = 20 in
tp = 1.0 in
Fy_pl = 50 ksi · A572 Gr.50
Anchors + Concrete
F1554-Gr36 1 in Ø
Ab = 0.7854 in² · Fy = 36 ksi
Fu = 58 ksi · 4× rods
f'c = 4 ksi · A2 = 400 in²
Factored Design Loads (LRFD)
Pu — Axial
300 kips
Mu — Moment
400 kip-ft
Vu — Shear
20 kips
Step 1 — Concrete bearing stress · ACI 318-22 §22.8.3.2
§22.8.3.2 — Bearing stress on concrete pedestal
ACI 318-22 §22.8.3.2 · φc = 0.65 · φPn ≥ Pu · Bearing stress = Pu / (N·B)
fc = Pu / (N · B) ≤ 0.85 · f'c
fc = 300 kips / (20 in · 20 in) = 300 / 400 = 0.75 ksi
φPn = φc · 0.85 · f'c · A1 = 0.65 · 0.85 · 4 · 400 = 884 kips
0.75 ksi < 0.85·4 = 3.40 ksi → PASS — 22% utilisation
Plate area A1 = N × B20 × 20 = 400 in²
Pedestal area A2 (same for uniform bearing)400 in²
Allowable bearing stress3.40 ksi
Actual bearing stress0.75 ksi
Utilisation = fc / (0.85·f'c)0.22 — 22%   PASS
Step 2 — Anchor rod tension · AISC 360-22 §J8
§J8 — Anchor rod tension from base moment (lever-arm method)
AISC 360-22 §J8 · T_i = Mu / (0.8 · d) per tension anchor · tension anchors = outer rods
// Moment creates tension in outer anchors (R1 and R4), compression in inner (R2 and R3)
T_per_anchor = Mu / (0.8 · d)
T = 400 kip-ft · 12 in/ft / (0.8 · 14.02 in) = 4800 / 11.22 = 42.8 kips per tension anchor
φRn (F1554-Gr36, 1 in Ø) = φ · Fy · Ab = 0.90 · 36 · 0.7854 = 25.5 kips
Utilisation = 42.8 / 25.5 = 1.68 → FAIL — Gr.36 understressed
// Escalate to F1554 Gr.55 — Fy = 55 ksi
φRn(Gr.55) = 0.90 · 55 · 0.7854 = 38.9 kips
Utilisation = 42.8 / 38.9 = 1.10 → FAIL — still over
// Escalate to F1554 Gr.105 — Fy = 105 ksi
φRn(Gr.105) = 0.90 · 105 · 0.7854 = 74.2 kips
Utilisation = 42.8 / 74.2 = 0.58 → PASS — 58%
Anchor tension utilisation (F1554-Gr.105, 1 in Ø)
0.58 — 58% ✓
Util. — 58% (max 100%)
  • Escalation: F1554-Gr.36 → Gr.55 fails (110%) → Gr.105 resolves at 58%
  • Embedment: Gr.105 requires min 12d = 12 in embedment per §IBC/ACI 318 anchor provisions
Step 3 — Anchor rod shear · AISC 360-22 §J3 / RCSC 2020
§J3 · RCSC 2020 — Nominal shear capacity of anchor rods
AISC 360-22 Table J3.2 · threads-in-shear (N) · φv = 0.65 for shear
V_per_anchor = Vu / n_anchors = 20 kips / 4 = 5.0 kips
Fnv (Gr.105 threads-in-shear) = 0.60 · Fu = 0.60 · 125 = 75 ksi
φVn = φv · 0.60 · Fu · Ab = 0.65 · 75 · 0.7854 = 38.3 kips per rod
Utilisation = 5.0 / 38.3 = 0.13 → 13% ✓ PASS
Anchor shear utilisation (F1554-Gr.105, 1 in Ø)
0.13 — 13% ✓
Util. — 13% (max 100%)
Step 4 — Combined tension + shear interaction · AISC 360-22 §J8.3
§J8.3 — Anchor rod combined T+V interaction (governing check)
AISC 360-22 §J8.3 · (T_i / φTn) + (V_i / φVn) ≤ 1.0
(T / φTn) + (V / φVn) ≤ 1.0
T = 42.8 kips   V = 5.0 kips   (tension anchor R1 or R4)
φTn = 0.90 · 105 · 0.7854 = 74.2 kips
φVn = 0.65 · 75 · 0.7854 = 38.3 kips
(42.8 / 74.2) + (5.0 / 38.3) = 0.577 + 0.131 = 0.708 ≤ 1.0
0.71 — 71% combined utilisation ✓ PASS
Combined T+V interaction (Gr.105, 1 in Ø)
0.71 — 71% ✓
Util. — 71% (max 100%)
Step 5 — Base plate thickness · AISC DG-1 Eq. 3.3.1–3.3.4
DG-1 (2nd Ed.) — Cantilever model for base plate bending
AISC DG-1 Eq. 3.3.1 · φ = 0.90 · Plate cantilever overhang m = (N − 0.95·d) / 2
m = (N − 0.95·d) / 2 = (20 − 0.95·14.02) / 2 = (20 − 13.32) / 2 = 3.34 in
n = (B − bf) / 2 = (20 − 14.52) / 2 = 2.74 in
fc_max = max( Pu/(N·B), 2·M/(3·B·n²) ) — bearing pressure on concrete
// Critical section at column flange — use cantilever m for governing direction
Mn = fc · m² / 2 = 0.75 · (3.34)² / 2 = 0.75 · 11.16 / 2 = 4.19 kip-in/in
tp ≥ √(2·Mn / (φ·Fy)) = √(2 · 4.19 / (0.90 · 50)) = √(0.186) = 0.43 in
Provided tp = 1.0 in > 0.43 in required — PASS — 43% utilisation on plate
Base plate thickness utilisation (provided 1.0 in)
0.43 — 43% ✓
Util. — 43% (max 100%)
Step 6 — Column-to-baseplate weld · AWS D1.1 §J2.4
§J2.4 — Fillet weld between column web/flanges and base plate
AWS D1.1 Table 3.1 · E70XX: FEXX = 70 ksi · CD = 1.43 for fillet welds · minimum 3/8 in
// Shear from Vu travels through column base as direct tension/compression in rods
φV_per_in = φ · 0.6 · FEXX · CD · 0.707 · a = 0.75 · 0.6 · 70 · 1.43 · 0.707 · (3/8) = 9.49 kip/in
V_per_in = Vu / (d + 2·bf) = 20 / (14.02 + 2·14.52) = 20 / 43.06 = 0.46 kip/in
Utilisation = 0.46 / 9.49 = 0.05 — 5% ✓ PASS (3/8 in E70XX fillet)
Column-to-baseplate weld — 3/8 in E70XX fillet
0.05 — 5% ✓
Util. — 5% (max 100%)
Summary — Connection BP1 · FrameAI Pro / Studio output
All checks pass — governing utilisation 71% (combined T+V)
Limit stateφRnDemandUtilisationRef
Concrete bearingφPn = 884 kipsPu = 300 kips0.34 — PASSACI 318-22 §22.8.3.2
Anchor tension — F1554-Gr.105 1 in ØφTn = 74.2 kipsT = 42.8 kips0.577 — PASSAISC 360-22 §J8
Anchor shear — F1554-Gr.105 1 in ØφVn = 38.3 kipsV = 5.0 kips0.131 — PASSAISC 360-22 §J3
Combined T+V (governing)—T=42.8 kip, V=5.0 kip0.708 — PASS§J8.3
Base plate thickness — 1 in A572 Gr.50φMn = 2.32 kip-in/inMn = 4.19 kip-in/in0.43 — PASSDG-1 Eq. 3.3.1
Column-to-plate weld — 3/8 in E70XX filletφV = 9.49 kip/inV = 0.46 kip/in0.05 — PASSAWS D1.1 §J2.4
// Design callout for fabrication drawing:
Joint BP1   W14×90 column   20×20×1 in A572 Gr.50 plate   4× F1554-Gr.105 1 in Ø anchors   3/8 in E70XX fillet weld (min)   embed ≥ 12d = 12 in
Run this on your drawing — upload PDF
FrameAI extracts column sizes from your PDF · auto-sizes the baseplate · runs all DG-1 checks · outputs fabrication-ready baseplate connection report with anchor schedule and weld callout
FrameAI Pro / Studio

Batch-design every baseplate in your drawing set — no manual calcs

FrameAI Pro uploads your entire drawing set as a PDF. It reads every column base, auto-sizes plate dimensions, runs AISC DG-1 / ACI 318 checks on all of them, flags the ones that fail, and produces a connection report PDF with anchor schedules and weld callouts. Batch upload, batch design, batch export.

Studio adds: DSTV NC1 fabrication files, IFC4 model export, clash detection, and a team workspace with revision history.

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Free resource

AISC 360-22 Connection Cheatsheet

A325/A490 bolt tables (½"–1¼"), E70XX weld strength per inch, prying action decision tree — 4 pages, imperial units.

Download the PDF →
← AISC Hub Samples Cheatsheet PDF Bolt Capacity Weld Sizing Endplate + Baseplate Calculator Endplate Moment
Baseplate Design
AISC DG-1 (2nd Ed.) Eq. 3.3.1–3.3.4
AISC 360-22 §J8 — Anchor tension
AISC 360-22 §J9 — Anchor provisions
Concrete Bearing
ACI 318-22 §22.8.3.2
φc = 0.65 · 0.85·f'c
Anchor Rods
ASTM F1554 Gr.36 / Gr.55 / Gr.105
RCSC 2020 — threads-in-shear