TheBridgeEng

Anchor Bolt Designer

Single cast-in headed anchor — tension & shear

All ACI-318-style failure modes for one cast-in headed bolt: steel, concrete breakout, pullout and pryout — with edge-distance and cracked-concrete effects, and the tension–shear interaction verdict.

Bolt

Grade (fᵤᵗₐ)

Concrete

Embedment hₑf150 mm

f′c

Edge cₐ₁ (shear dir.)150 mm

Edge cₐ₂ (perp.)far

Member depth h400 mm

Tension Nᵤ30 kN

Shear Vᵤ20 kN

Tension φNₙ

Shear φVₙ

Basis (SI, N–mm): φNₛₐ=0.75Aₛₑfᵤᵗₐ; Nₒ=10√f′c·hₑf¹⋅⁵ with Aₖc/Aₖco, ψₑd, ψc (1.0 cracked / 1.25 uncracked), φ=0.70; pullout 0.70·8Aₒᵣg·f′c; φVₛₐ=0.65·0.6Aₛₑfᵤᵗₐ; edge breakout Vₒ toward cₐ₁ with thickness and perpendicular-edge factors; pryout kₛₓ=1 (hₑf<65) or 2. Trilinear interaction N/φNₙ+V/φVₙ≤1.2. Aₛₑ=0.75·πd²/4 (coarse thread approx.), Aₒᵣg from standard heavy-hex heads. Verified against an independent Python implementation on 300 randomised cases (≤10⁻⁹) and hand-checked spot values. Not covered: anchor groups, eccentricity, supplementary reinforcement, seismic Ωₐ, stand-off, adhesive/expansion anchors. Preliminary design only.

Field notes — what to watch for

Concrete breakout, not steel, governs most real anchors — embedment depth and edge distance are the design variables that matter. If you can, size the anchor so steel governs: that failure is ductile and visible. Everything here is a single anchor; groups interact through overlapping cones and need the full Chapter 17 treatment.

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