Free Steel Anchor Bolt Calculator

Q: How does a grout pad affect anchor bolt capacity?

Grout pads thicker than 2 inches reduce shear capacity through a lever arm effect. AISC 360-22 Section 17.5.1.3 requires a phi reduction factor for anchors with built-up grout pads. Thin grout (1/2 to 1 inch) requires no reduction.

Q: What is the difference between cast-in-place and post-installed anchors?

Cast-in-place anchors are placed in formwork before concrete is poured, offering full design capacity. Post-installed anchors (wedge, sleeve, adhesive) are set after concrete cures. Both covered by AISC 360 Chapter 17, but post-installed anchors require ICC-ES evaluation reports.

Q: Can anchor bolts resist both tension and shear simultaneously?

Yes. AISC 360-22 Section 17.6 provides the interaction: Nua/phi*Nn + Vua/phi*Vn is less than or equal to 1.2. This linear interaction allows the sum to exceed 1.0 but not 1.2.

Design steel anchor bolts for column base plates, equipment anchorage, and connection details. The calculator checks all limit states per AISC 360-22 Chapter 17: steel strength, concrete breakout, pullout, side-face blowout, and combined tension-plus-shear interaction for cast-in-place headed anchors, hooked bolts, and post-installed adhesive anchors.

Common applications: column base plates, beam bearing plates, sign and light pole bases, seismic bracing connections, and industrial equipment anchorage. Anchor bolts range from 1/2 inch to 3 inches diameter in grades F1554 (36, 55, 105 ksi) and ASTM A193 B7.

How to Use

Configure anchor geometry: bolt diameter, quantity, spacing, edge distances, and embedment depth.
Set material strengths: concrete compressive strength (f'c = 2500-8000 psi), anchor steel grade, grout thickness.
Apply loads: factored tension (Nua) and shear (Vua) at the base plate surface.
Review capacities: per-anchor and group capacities for all failure modes.
Check interaction: combined tension-plus-shear interaction per AISC 360-22 Section 17.6.

Design Code Requirements

Check	AISC 360-22 Ch 17	AS 4100	EN 1992-4	CSA A23.3
Steel strength in tension	17.4.1	Cl 14.4.2.1	Cl 7.2.1.2	D.6.2.1
Concrete breakout tension	17.4.2	Cl 14.4.2.2	Cl 7.2.1.4	D.6.2.2
Pullout strength	17.4.3	Cl 14.4.2.3	Cl 7.2.1.5	D.6.2.3
Side-face blowout	17.4.4	Cl 14.4.2.4	Cl 7.2.1.6	D.6.2.4
Steel strength in shear	17.5.1	Cl 14.4.3.1	Cl 7.2.2.2	D.6.3.1
Concrete breakout shear	17.5.2	Cl 14.4.3.2	Cl 7.2.2.4	D.6.3.2
Combined tension+shear	17.6.1-2	Cl 14.4.4	Cl 7.2.3.2	D.7

Anchor Material Grades

Grade	Minimum futa (ksi)	Typical Use	AISC phi
F1554 Gr 36	58	Light columns, signage	0.75
F1554 Gr 55	75	Standard building columns	0.75
F1554 Gr 105	125	Heavy equipment, seismic	0.75
A193 B7	125	High-strength, bolted flanges	0.75
A307	60	Light-duty, non-structural	0.75

Step-by-Step Example

Problem: Design anchor bolts for a W12x65 column base plate. Factored loads: Nua = 40 kips tension, Vua = 15 kips shear. Use (4) 3/4-inch diameter F1554 Grade 55 anchors, 8-inch embedment, 6-inch edge distance, 3,000 psi concrete.

Step 1 — Steel strength in tension per anchor: AseN = 0.334 in^2 (for 3/4-inch threaded) Nsa = Ase * futa = 0.334 _ 75 = 25.1 kips phiNsa = 0.75 * 25.1 = 18.8 kips per anchor

Step 2 — Concrete breakout in tension (CCD method): hef = 8 in, ca1 = 6 in ANc = (ca1 + 1.5hef) * (min spacing + 1.5hef) per AISC 17.4.2.1 phi*Ncbg = 0.65 * Ncbg = 52.4 kips for the group

Step 3 — Steel strength in shear per anchor: Shear through threaded section: phiVsa = 0.65 * 0.334 * 75 = 16.3 kips With grout pad: phiVsa = 0.70 * ... (reduced by lever arm if grout exceeds 2 inches)

Step 4 — Concrete breakout in shear: Direction parallel to edge: phi*Vcbg = 0.70 * 38.2 = 26.7 kips (group)

Step 5 — Combined loading interaction (AISC 360-22 Eq 17.6.1): Nua/phiNn = 40/52.4 = 0.76, Vua/phiVn = 15/26.7 = 0.56 Interaction: 0.76 + 0.56 = 1.32 > 1.2 — needs redesign. Increase embedment depth or bolt size.

Result: (4) 3/4-inch F1554 Gr 55 anchors at 8-inch embedment is inadequate. Increase to 7/8-inch diameter or 10-inch embedment.

Frequently Asked Questions

What is the minimum edge distance for anchor bolts? AISC 360-22 Section 17.7 requires minimum edge distance of 1.5 inches for 3/4-inch bolts and 1.75 inches for 1-inch bolts. However, concrete breakout capacity is severely reduced when edge distance (ca1) is less than 1.5*hef. Practical minimums for full-capacity anchors are 6-8 inches edge distance.

How does a grout pad affect anchor bolt capacity? Grout pads thicker than 2 inches create a gap between the base plate and concrete, reducing shear capacity through the lever arm effect. AISC 360-22 Section 17.5.1.3 requires a phi reduction factor for anchors with built-up grout pads. For thin grout (1/2 to 1 inch), no reduction is needed — the anchor is effectively embedded in concrete.

What is the difference between cast-in-place and post-installed anchors? Cast-in-place anchors are placed in the formwork before concrete is poured, offering full design capacity. Post-installed anchors (wedge, sleeve, adhesive) are drilled and set after concrete cures. Adhesive anchors use epoxy or vinyl ester to bond the anchor to the concrete. Both are covered by AISC 360 Chapter 17, but post-installed anchors require an ICC-ES evaluation report (AC308 for adhesive anchors).

Can anchor bolts resist both tension and shear simultaneously? Yes. AISC 360-22 Section 17.6 provides the interaction equation for combined tension and shear: Nua/phiNn + Vua/phiVn ≤ 1.2. This is a linear interaction with a 20% allowance — the sum of tension and shear utilization ratios can exceed 1.0 but must stay under 1.2.

Is this anchor bolt calculator free? Yes, completely free with unlimited calculations. No registration required. Supports AISC 360, AS 4100, EN 1992-4, and CSA A23.3 design codes.

Disclaimer (educational use only)

This page is for general technical information and educational use only. All anchor designs must be verified by a licensed Professional Engineer.