Free Anchor Embedment Calculator

Calculate the required embedment depth for cast-in-place and post-installed anchor bolts in concrete using the concrete capacity design (CCD) method. The calculator checks tension and shear capacities across concrete breakout, pullout, pryout, and side-face blowout failure modes per AISC 360-22 Chapter 17, AS 4100, EN 1992-4, and CSA A23.3.

Typical embedment depths range from 4 to 12 bolt diameters (db) for standard steel column base plates. A 3/4-inch diameter anchor bolt (F1554 Grade 36) embedded 6 inches in 3,000 psi concrete provides approximately 12-15 kips tension capacity, depending on edge distance and spacing conditions.

How to Use

  1. Select anchor type: cast-in-place headed stud, cast-in-place hooked bolt, or post-installed adhesive anchor.
  2. Enter anchor geometry: diameter, effective embedment depth (hef), edge distances, and spacing.
  3. Specify material properties: concrete compressive strength (f'c), anchor steel grade (F1554 Gr 36/55/105, A193 B7, or ASTM F593).
  4. Apply loads: factored tension (Nua) and shear (Vua) demands.
  5. Review results: governing failure mode, design strength (phiNn / phiVn), and utilization ratio.

Design Code Requirements

Check AISC 360-22 Ch 17 AS 4100 EN 1992-4 CSA A23.3
Concrete breakout tension 17.4.2 (CCD method) Cl 14.4.2.2 Cl 7.2.1.4 Cl D.6.2.2
Concrete breakout shear 17.5.2 Cl 14.4.3.2 Cl 7.2.2.4 Cl D.6.3.2
Pullout strength 17.4.3 Cl 14.4.2.3 Cl 7.2.1.5 Cl D.6.2.3
Side-face blowout 17.4.4 Cl 14.4.2.4 Cl 7.2.1.6 Cl D.6.2.4
Steel strength tension 17.4.1 Cl 14.4.2.1 Cl 7.2.1.2 Cl D.6.2.1
Concrete pryout (shear) 17.5.3 Cl 14.4.3.3 Cl 7.2.2.5 Cl D.6.3.3
Combined tension+shear 17.6 Cl 14.4.4 Cl 7.2.3 Cl D.7
phi factors (tension) 0.75 (steel), 0.65 (concrete) 0.80 1.5 (gamma_Mc) 0.85

Key difference: EN 1992-4 uses partial safety factors (gamma_Mc = 1.5 for concrete, gamma_Ms = 1.2 for steel), while AISC 360 applies phi factors (0.75 for ductile steel, 0.65 for concrete breakout). AS 4100 uses capacity factor phi = 0.80 for all anchor failure modes.

Step-by-Step Example

Problem: Determine the tension capacity of a 3/4-inch diameter cast-in-place headed anchor bolt (F1554 Grade 36) embedded 6 inches in 3,000 psi normal-weight concrete. Edge distance = 6 inches in both directions (corner condition). No adjacent anchors.

Step 1 — Steel strength (AISC 360-22 Eq 17.4.1.2): Nsa = Ase _ futa = 0.334 _ 58,000 = 19,372 lb = 19.4 kips phi*Nsa = 0.75 * 19.4 = 14.5 kips

Step 2 — Concrete breakout strength (AISC 360-22 Eq 17.4.2.1b): ANc = (c1 + 1.5hef) * (c2 + 1.5hef) = (6 + 9) * (6 + 9) = 225 in^2 ANco = 9 _ hef^2 = 9 _ 36 = 324 in^2 ANc/ANco = 225/324 = 0.694

psi = sqrt(6) / 1.5 = 1.63 (edge effect for corner, ca1 = 6 in)

Nb = kc _ lambda_a _ sqrt(f'c) _ hef^1.5 = 24 _ 1.0 _ sqrt(3000) _ 6^1.5 Nb = 24 _ 54.77 _ 14.70 = 19,310 lb = 19.3 kips

Ncbg = (ANc/ANco) _ psi _ Nb = 0.694 _ 1.63 _ 19.3 = 21.8 kips phi*Ncbg = 0.65 * 21.8 = 14.2 kips

Step 3 — Pullout strength (AISC 360-22 Eq 17.4.3.1): Npn = 8 _ Abrg _ f'c = 8 _ 0.442 _ 3000 = 10,608 lb = 10.6 kips phi*Npn = 0.70 * 10.6 = 7.4 kips

Step 4 — Governing tension capacity: Governing = min(14.5, 14.2, 7.4) = 7.4 kips (pullout governs)

Result: Design tension capacity = 7.4 kips. Pullout governs — consider increasing embedment depth or using a larger head to increase bearing area.

Frequently Asked Questions

What is the minimum embedment depth for anchor bolts in steel construction? For cast-in-place headed anchor bolts, the minimum effective embedment (hef) is typically 4 bolt diameters (4db) or 2 inches, whichever is greater. In seismic applications (AISC 341), a minimum of 12db may be required to ensure ductile behavior. For post-installed anchors, follow the manufacturer's published ICC-ES ESR report for minimum embedment.

How does edge distance affect anchor embedment capacity? Edge distance is one of the most influential parameters. At edge distances less than 1.5 * hef, the concrete breakout cone is truncated by the free edge, reducing capacity below the full breakout strength. At very small edge distances (under 3-4 inches), side-face blowout may govern for deep embedments. Increasing edge distance by even 1 inch can significantly improve capacity — typically by 10-20% for anchors near the edge.

What is the difference between concrete breakout and pullout failure? Concrete breakout is a cone-shaped failure propagating from the embedded head to the concrete surface at roughly a 35-degree angle. It depends on embedment depth and edge distance. Pullout is the anchor pulling the head through the concrete without surface breakout — it is governed by the bearing area of the head and concrete compressive strength. Pullout typically governs for shallow embedments or small headed areas, while breakout governs for deeper embedments.

Which design standard covers anchor bolt embedment? AISC 360-22 Chapter 17 (formerly Appendix D) covers anchor design in the US. EN 1992-4 governs in Europe. AS 4100 Section 14 covers in Australia, and CSA A23.3 Annex D covers in Canada. All four standards use the concrete capacity design (CCD) method with a 35-degree breakout cone, but differ in resistance factors and edge effect equations.

Is this anchor embedment calculator free to use? Yes, completely free with unlimited calculations. No registration or account required. Use it for preliminary anchor sizing, embedment depth checks, and design verification across AISC 360, AS 4100, EN 1992-4, and CSA A23.3.

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Disclaimer (educational use only)

This page is provided for general technical information and educational use only. It does not constitute professional engineering advice. All structural designs must be verified by a licensed Professional Engineer (PE) or Structural Engineer (SE). The site operator disclaims liability for any loss or damage arising from the use of this page.