---------------------- | ----------------- | ----------- | ---------- | --------- | | 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

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.

Design Guidance

Key Design Parameters

When performing structural steel design calculations, the following parameters govern the design:

• Material properties: Yield strength (Fy) and tensile strength (Fu) determine section capacity. For US projects, common grades include A992 (Fy=50 ksi) for W-shapes and A36 (Fy=36 ksi) for angles and plates.
• Design method: LRFD (Load and Resistance Factor Design) or ASD (Allowable Stress Design). LRFD applies load factors >1.0 and resistance factors <1.0 for consistent reliability across limit states.
• Load combinations: Per ASCE 7-22, the governing combination depends on the direction and magnitude of each load type. Typically 1.2D + 1.6L governs for gravity-dominated cases.
• Limit states: Strength (ultimate) and serviceability (deflection, vibration). Both must be checked per the applicable design code.
• Applicable codes: AISC 360-22 (US), EN 1993-1-1 (EU), AS 4100 (Australia), CSA S16 (Canada).

Design Procedure

1. Establish design criteria: code edition, material grade, design method (LRFD/ASD)
2. Determine loads and applicable load combinations
3. Analyze structure for internal forces (axial, shear, moment, torsion)
4. Check member strength for all applicable limit states
5. Verify serviceability criteria (deflection, drift, vibration)
6. Detail connections to transfer calculated forces

Worked Example

Problem: Design a structural element for the following conditions:

Span/Height: 15 ft | Load: 50 kips (factored) | Section: W12×65 (A992, Fy=50 ksi) | Code: AISC 360-22 LRFD

Solution:

• Demand: Pu = 50 kips (axial compression)
• Section properties: A = 19.1 in², rx = 5.28 in, ry = 3.02 in
• Slenderness: KL/r = 1.0 × 15 × 12 / 3.02 = 59.6 (controls about weak axis)
• Critical stress: Fcr per AISC Eq E3-2 (intermediate slenderness range)
• Design strength: φcPn = 0.9 × Fcr × Ag — Verify against applied load
• Interaction: Check combined forces per AISC Chapter H if applicable

Result: Section is adequate if φcPn ≥ Pu (50 kips).

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.

Related pages

• Anchor embedment calculator
• Base plate design calculator
• Steel column base design
• Bolt torque calculator
• Anchor bolts reference

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.