--------- | -------------- | --------------- | ------------- | ------------------------ | | Bearing-type | Permitted | NOT permitted | NOT permitted | NOT permitted | | Slip-critical | Permitted | Permitted | Permitted | Permitted (one ply only) | | Tension-only | Permitted | Permitted | Permitted | Case-by-case |

Key points:

• Bearing-type connections (most common): ONLY standard holes are permitted. No oversized holes.
• Slip-critical connections: Oversized holes are permitted, but require hardened washers (F436) and proper pretensioning
• The reason is simple: oversized holes allow bolt movement, which is unacceptable when the bolt bears against the hole edge to transfer shear

Oversized Hole Dimensions (AISC Table J3.3)

Bolt Bearing and Tearout Compliance

Bearing Strength at Bolt Holes

Per AISC 360-22 Section J3.10:

For standard holes (deformation at service load is a concern):

φRn = φ × 1.2 × Lc × t × Fu (φ = 0.75)

For standard holes (deformation is NOT a concern):

φRn = φ × 1.5 × Lc × t × Fu (φ = 0.75)

For oversized or slotted holes:

Use a reduced coefficient (see AISC Table J3.10).

Lc = clear distance between the edge of the hole and the edge of the adjacent hole or edge of material.

Tearout Check

Tearout occurs when the material behind the bolt shears out along two parallel planes:

φRn = φ × 1.2 × Lc × t × Fu (same as bearing, but Lc is the edge distance)

If tearout governs, increase edge distance or add more bolts.

Minimum Edge Distance Compliance

Per AISC Table J3.4M:

These are minimums. Bearing capacity may require larger edge distances.

Weld Compliance Checks

Minimum Fillet Weld Size (AISC Table J2.4)

This is a prescriptive minimum for heat input and fusion, not a strength requirement.

Fillet Weld Strength

φRn = φ × 0.60 × FEXX × (0.707 × w) × L (φ = 0.75)

where:

• FEXX = electrode classification strength (e.g., 70 ksi for E70XX)
• w = fillet weld leg size
• L = effective weld length (actual length minus 2 × w for start/stop craters)
• 0.707 = converts leg size to throat size for equal-leg fillet

E70XX Weld Strength

For E7018 (most common structural electrode):

• FEXX = 70 ksi (483 MPa)
• Fillet weld shear strength = 0.60 × 70 = 42 ksi
• Design shear strength per 1/16 inch of leg per inch of length = 0.928 kips/in

Maximum Weld Size

Along edges of material:

• Material < 1/4 inch thick: max weld size = material thickness
• Material ≥ 1/4 inch thick: max weld size = material thickness - 1/16 inch

Slip-Critical Connection Compliance

When Slip-Critical is Required

Per AISC Section J3.1, slip-critical connections are required for:

1. Connections subject to fatigue loading with reversal of load direction
2. Joints where bolts connect to oversized holes or slotted holes with loads parallel to the slot
3. Joints where slip would compromise the structural integrity

Pretensioning Requirements

Pretension = 0.70 × Fnt × Ab

Installation Methods

1. Turn-of-nut: Rotate the nut a specified number of turns from snug-tight (typically 1/3 to 1 full turn depending on bolt length and geometry)
2. Calibrated wrench: Torque to achieve required pretension (requires daily calibration)
3. Direct tension indicators (DTI): Compressible washers that indicate proper tension
4. Twist-off bolts: Bolt has a spline that shears off at the correct tension

Faying Surface Requirements

For slip-critical connections, the faying surfaces must meet specific requirements:

Painted surfaces: verify slip coefficient with manufacturer data. Most standard paints reduce μ to 0.05-0.15, effectively preventing slip-critical behavior.

Connection Design Checklist — Code Compliance

• Bolt type specified (A325, A490, Grade 8.8) and matched to application
• Hole type matches connection type (standard for bearing, oversized only for slip-critical)
• Proper washers specified (F436 for oversized holes, hardened for pretensioning)
• Edge distances ≥ minimum per AISC Table J3.4
• Bolt spacing ≥ 2.67d center-to-center
• Bearing capacity checked per AISC J3.10
• Tearout capacity checked for all bolts near edges
• Fillet weld size ≥ minimum per Table J2.4
• Fillet weld throat provides adequate strength
• Weld length ≥ 4w (minimum effective length)
• Slip-critical designation applied where required
• Faying surface class specified (A, B, or C)
• Pretensioning method specified for slip-critical connections
• Shop drawing notes include all connection requirements

Frequently Asked Questions

Can I use a nut as a washer? No. Per AISC 360-22, standard F436 hardened washers must be used under nuts and bolt heads, especially for oversized holes. Nuts do not provide the correct bearing area, hardness, or flatness.

When are oversized holes permitted? Only in slip-critical connections. Bearing-type connections must use standard holes. Oversized holes are also permitted in tension-only connections at the discretion of the engineer.

What is the minimum fillet weld size for 1/2 inch plate? 3/16 inch per AISC Table J2.4. This ensures adequate heat input and fusion.

How do I check bolt bearing? Calculate φRn = 0.75 × 1.2 × Lc × t × Fu where Lc is the clear distance from hole edge to adjacent hole or material edge. Verify φRn ≥ required shear per bolt.

What is the slip coefficient for galvanized connections? Class B: μ = 0.50 for hot-dip galvanized and roughened surfaces. Untreated galvanized surfaces may have lower slip coefficients.

What weld electrode should I use for A992 steel? E7018 (SMAW) or E70T-1 (FCAW) with FEXX = 70 ksi. The electrode strength should match or exceed the base metal strength requirements.

Try it now: Check your connection code compliance with our free Bolted Connection calculator →

Related Pages

• Bolted Connections Calculator — Automated AISC bolt checks
• Welded Connections Calculator — Fillet and groove weld capacity
• Bolt Hole Sizes — Standard hole dimension tables
• Bolt Bearing & Tearout — Bearing and tearout calculations
• Min Weld Size — Minimum weld size by material thickness
• Bolt Grades — A325, A490, Grade 8.8 properties
• Connection Types — Shear, moment, and specialty connections

Disclaimer

This is a calculation tool, not a substitute for professional engineering certification. All results must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) before use in construction, fabrication, or permit documents. The user is responsible for the accuracy of all inputs and the verification of all outputs.

Design Resources

Calculator tools

• Bolted Connection Calculator
• Weld Capacity Calculator
• End Plate Moment Connection Calculator
• Fin Plate Shear Connection Calculator
• Gusset Plate Calculator

Design guides

• Bolted Connection Worked Example
• Bolted Connection Checklist
• Steel Connection Calculator Guide
• Weld Design Checklist
• EN 1993-1-8 Bolted Connection Worked Example

Reference pages

• Shear Tab