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Anchor Bolt & Base Plate

Concentric base plate sizing (LRFD) per AISC, anchor tension and shear demand from column moment, plus ACI 318 Ch. 17 concrete breakout/pull-out checks.

Inputs

Loads (LRFD)

kN (compression +)
kN·m
kN

Plate & Column

mm (parallel to M)
mm
MPa (A36 ≈ 250)
mm (W shape)
mm
MPa

Anchors

mm
mm
MPa (A325/F1554 Gr 105 ≈ 800)
mm
mm (between rows)
Method & assumptions
  • Eccentricity e = Mu/Pu; if e ≤ N/6, plate in compression only (no anchor tension).
  • If e > N/6, simplified bolt-tension model: Y = bearing length (computed iteratively); T = tension in anchor row.
  • Plate thickness: tp = √(2·m²·fp/(0.9·Fy)) using cantilever m or n at controlling face.
  • Anchor tension capacity (steel): φNsa = φ·n·Ase,N·futa; φ = 0.75.
  • Concrete breakout (single anchor): Ncb = (ANc/ANco)·ψ·Nb; Nb = kc·λ·√f'c·hef1.5; kc=10 cast-in, MPa.
  • Anchor shear capacity: φVsa = φ·n·0.6·Ase,V·futa; φ = 0.65.

Results

Eccentricity e = M/P
N/6 kern
Concrete bearing fp
Anchor tension demand Tu
Plate thickness tp (req.)
Anchor steel φNsa
Concrete breakout φNcb
Anchor steel φVsa
Tension checkOK
Shear checkOK