Bolt Bearing and Tearout — AISC 360 Section J3.10 Reference

Bearing and tearout are limit states at bolt holes where the bolt pushes against the plate material. Bearing failure involves localized crushing of the plate behind the bolt, while tearout is a shear rupture along the edge of the plate from the bolt hole to the nearest free edge. Both must be checked for every bolt in a bearing-type connection per AISC 360-22 Section J3.10.

Bearing vs. tearout

Bearing is the compressive crushing of plate material immediately behind the bolt hole. The bolt pushes against the plate, and if the plate is too thin or the bolt load too high, the plate deforms excessively (hole elongation > 1/4"). Bearing capacity depends on bolt diameter, plate thickness, and plate ultimate strength.

Tearout (also called bolt-hole tear-out or edge shear) is a shear rupture failure where the plate material between the bolt hole and the nearest edge shears out in two parallel planes. Tearout governs when the bolt is close to an edge or when bolts are closely spaced.

For every connection, check both bearing and tearout for each bolt individually. The capacity of each bolt is the lesser of the two values, and the connection capacity is the sum of individual bolt capacities.

AISC 360-22 Section J3.10 equations

Bearing (deformation a design consideration):

phiRn = phi * 2.4 * d * t * Fu     (phi = 0.75)

Bearing (deformation not a design consideration):

phiRn = phi * 3.0 * d * t * Fu     (phi = 0.75)

Tearout:

phiRn = phi * 1.2 * Lc * t * Fu    (phi = 0.75)

Where d = bolt diameter, t = connected plate thickness, Fu = plate ultimate tensile strength, and Lc = clear distance from hole edge to plate edge or adjacent hole edge in the direction of force.

For each bolt: phiRn = min(bearing, tearout). For end bolts with small edge distances, tearout almost always governs. For interior bolts with standard spacing, bearing usually governs.

Bearing capacity per bolt — 3/4" bolts (phi = 0.75)

Bearing capacity per bolt — by diameter, A36 plate, 3/8" thick

Calculating clear distance (Lc)

End bolt (nearest to plate edge):

Lc = Le - dh/2

Where Le = edge distance (bolt center to plate edge), dh = hole diameter.

Interior bolt (between other bolts):

Lc = s - dh

Where s = center-to-center bolt spacing in the direction of force.

Hole diameters for standard bolts (AISC Table J3.3)

Clear distance (Lc) table for 3/4" bolts

Critical threshold: Tearout governs when Lc < 2*d. For 3/4" bolts, this is Lc < 1.5 in.

Worked example — 3-bolt lap splice

Given: 3 bolts in a line, 3/4" A325-N single shear, 3/8" A36 plate (Fu = 58 ksi), edge distance 1.25", spacing 3", standard holes.

Bolt shear: phiRv = 0.75 _ 54 _ 0.442 = 17.9 kips/bolt.

End bolt: Lc = 1.25 - 0.406 = 0.844 in. Bearing: 0.75*2.4*0.75*0.375*58 = 29.3 kips. Tearout: 0.75*1.2*0.844*0.375*58 = 16.5 kips. Governs: tearout = 16.5 kips.

Interior bolts (2): Lc = 3.0 - 0.8125 = 2.1875 in. Bearing: 29.3 kips. Tearout: 0.75*1.2*2.1875*0.375*58 = 42.8 kips. Governs: bearing = 29.3 kips.

Connection capacity (bearing/tearout): 16.5 + 29.3 + 29.3 = 75.1 kips.

Connection capacity (bolt shear): 3 * 17.9 = 53.7 kips.

Governing: Bolt shear = 53.7 kips. Even though bolt shear governed here, the end-bolt tearout (16.5 kips) was less than bolt shear (17.9 kips). Any smaller edge distance and tearout would govern.

Worked example — when tearout governs the connection

Given: 2 bolts, 3/4" A325-N, 3/8" A36 plate, edge distance Le = 1.0" (AISC minimum), spacing 3".

End bolt: Lc = 1.0 - 0.406 = 0.594 in. Tearout: 0.75*1.2*0.594*0.375*58 = 11.6 kips. Bearing: 29.3 kips. Tearout = 11.6 kips governs.

Interior bolt: Lc = 3.0 - 0.8125 = 2.188 in. Tearout: 42.8 kips. Bearing: 29.3 kips. Bearing = 29.3 kips governs.

Connection capacity (bearing/tearout): 11.6 + 29.3 = 40.9 kips.

Connection capacity (bolt shear): 2 * 17.9 = 35.8 kips.

Governing: Bolt shear at 35.8 kips, but end-bolt tearout (11.6 kips) is very low. If edge distance were increased to 1.5", tearout becomes 21.4 kips > bolt shear 17.9 kips, and bolt shear fully governs. This is why practical design uses 1.5d edge distance.

Bearing/tearout for oversize and slotted holes

Larger hole diameters increase the hole deduction and reduce Lc, making tearout more likely to govern.

Long slots in the direction of force dramatically reduce tearout capacity. For a 3/4" bolt with long slot at Le = 1.25", tearout = 0.75*1.2*0.313*0.375*58 = only 6.1 kips per bolt.

Multi-code comparison

AS 4100-2020 Clause 9.2.2.4 uses Vb = 3.2*df*tp*fup for bearing per bolt. Edge tearout is controlled primarily through minimum edge distance requirements (Table 9.3.2). The bearing coefficient of 3.2 is comparable to AISC's 3.0 (deformation not a concern).

EN 1993-1-8 integrates bearing and tearout into a single equation: Fb,Rd = (k1*alpha_b*fu*d*t)/gamma_M2, where alpha_b = min(alpha_d, fub/fu, 1.0) and alpha_d depends on edge distance and spacing ratios.

Cross-code capacity comparison: 3/4" bolt, 3/8" A36 plate, Le = 1.25", s = 3"

AISC 360-22 Section J3.10: Bearing and Tearout Procedure

AISC 360 Section J3.10 defines two limit states for bolted connections loaded in shear: bolt bearing on the connected material and tearout (also called "bolt tearout" or "edge tearout"). Both must be checked for every bolt in the connection.

Step-by-Step Procedure

Step 1: Determine the clear distance Lc from the edge of the bolt hole to the nearest edge of the adjacent hole or to the free edge of the connected part, in the direction of the applied force.

Lc = Le - dh/2        (for end bolt, edge distance Le)
Lc = s - dh            (for interior bolt, spacing s)

Where dh is the bolt hole diameter per AISC Table J3.3 (standard hole: dh = d + 1/16 in).

Step 2: Compute the bearing strength (deformation is a design consideration):

phi * Rn = phi * 2.4 * d * t * Fu    (AISC Eq. J3-6a)

Step 3: Compute the tearout strength (deformation is a design consideration):

phi * Rn = phi * 1.2 * Lc * t * Fu    (AISC Eq. J3-6b)

Step 4: If deformation at the bolt hole is NOT a design consideration (acceptable hole elongation):

Bearing:  phi * Rn = phi * 3.0 * d * t * Fu   (AISC Eq. J3-6c)
Tearout:  phi * Rn = phi * 1.5 * Lc * t * Fu   (AISC Eq. J3-6d)

Step 5: The governing capacity per bolt is the minimum of bearing and tearout. Sum over all bolts to get total connection capacity.

Deformation vs. Tearout Equations Comparison

The "deformation is a concern" equations (2.4 and 1.2) limit hole elongation to approximately 1/4 in at service loads. The "not a concern" equations (3.0 and 1.5) allow larger deformation but provide higher capacity.

Edge Distance Effects on Tearout Capacity

The following table shows how edge distance (Le) directly affects tearout capacity for a 3/4 in diameter bolt in 3/8 in A36 plate (Fu = 58 ksi, dh = 13/16 in).

Key observation: For 3/4 in bolts, bearing governs when Le >= 1.5 in. At the AISC minimum edge distance of 1.0 in, tearout capacity is only 53% of bearing capacity.

Worked Example: Bolt Bearing and Tearout

Problem: A lap splice connection uses (4) 3/4 in A325 bolts in standard holes, connecting two A36 plates (Fy = 36 ksi, Fu = 58 ksi). The plates are 3/8 in thick. Bolt spacing is 3 in. Edge distance at the end is 1.25 in. Applied shear = 65 kips.

Step 1: Bolt hole diameter

dh = d + 1/16 = 3/4 + 1/16 = 13/16 = 0.8125 in

Step 2: Clear distances

End bolt (bolt 1): Lc1 = Le - dh/2 = 1.25 - 0.406 = 0.844 in
Interior bolt (bolts 2-4): Lc = s - dh = 3.0 - 0.8125 = 2.1875 in

Step 3: Bearing capacity per bolt (deformation IS a concern)

phi * Rn_bearing = 0.75 * 2.4 * d * t * Fu
                = 0.75 * 2.4 * 0.75 * 0.375 * 58
                = 0.75 * 39.15 = 29.4 kips per bolt (same for all bolts)

Step 4: Tearout capacity per bolt

End bolt: phi * Rn_tearout = 0.75 * 1.2 * Lc1 * t * Fu
                            = 0.75 * 1.2 * 0.844 * 0.375 * 58
                            = 0.75 * 22.1 = 16.6 kips

Interior bolts: phi * Rn_tearout = 0.75 * 1.2 * 2.1875 * 0.375 * 58
                                  = 0.75 * 57.2 = 42.9 kips

Step 5: Governing capacity per bolt

End bolt: min(29.4, 16.6) = 16.6 kips (tearout governs)
Interior bolts: min(29.4, 42.9) = 29.4 kips (bearing governs)

Step 6: Total connection capacity

phi * Rn_total = 16.6 + 29.4 + 29.4 + 29.4 = 104.8 kips

Step 7: Check demand

Pu = 65 kips < phi * Rn = 104.8 kips  --> OK (utilization = 62%)

If all four bolts were end bolts (Lc = 0.844), total capacity = 4 * 16.6 = 66.4 kips -- barely adequate. The end bolt tearout is clearly the weak link. Increasing the edge distance to 2.0 in would raise the end bolt capacity to 31.3 kips (bearing governs), increasing total capacity to 31.3 + 29.4 + 29.4 + 29.4 = 119.5 kips.

Common mistakes

1. Not checking each bolt individually. End bolts have shorter Lc values and lower tearout capacities than interior bolts.

2. Using bolt diameter instead of hole diameter for Lc. Clear distance is from the hole edge, not the bolt edge. Using d instead of dh overestimates Lc.

3. Confusing edge distance with clear distance. Edge distance Le is from bolt center to plate edge. Clear distance Lc = Le - dh/2.

4. Forgetting to check both plates. In a lap splice, both plates must be checked. The thinner plate or shorter edge distance governs.

5. Applying the 3.0 factor universally. The 3.0*d*t*Fu formula is only valid when deformation is not a concern. Most building connections use the 2.4 factor.

6. Using dh = d + 1/16 for all hole types. Standard holes are d + 1/16, but oversize, short-slot, and long-slot holes have different dimensions per AISC Table J3.3.

7. Not checking tearout in both directions. For connections with forces at an angle to the bolt line, Lc must be checked in the direction of the resultant force, not just along the bolt line.

Frequently asked questions

When does tearout govern over bearing? Tearout governs when Lc is small -- typically for end bolts with Le < 1.5d or closely spaced bolts with s < 3d. Quick check: tearout governs when Lc < 2d.

What is the minimum edge distance to avoid tearout problems? AISC Table J3.4 minimums (e.g., 1" for 3/4" bolt) can result in tearout governing. For practical design, use 1.5d edge distance to ensure bearing governs. For 3/4" bolts, use Le >= 1.125".

Do I check bearing for slip-critical connections? Yes. Bearing/tearout is checked as an ultimate limit state even for slip-critical connections. If slip occurs, the bolts go into bearing.

What if deformation is not a concern? Use the 3.0 coefficient instead of 2.4. This allows 25% more bearing capacity but accepts that the hole may elongate beyond 1/4" at service loads. Common in bearing connections for temporary structures or where appearance is not critical.

Does plate grade affect bearing capacity? Yes, directly. Bearing and tearout are both proportional to Fu. A572 Gr 50 (Fu = 65 ksi) gives 12% more capacity than A36 (Fu = 58 ksi) for the same geometry.

How do I check bearing for a connection with multiple bolt rows? Each bolt row may have different Lc values if the edge distances or spacings differ. Check each bolt individually, sum the minimum of bearing and tearout for each bolt, and compare to the applied shear per bolt.

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Related references

• Bolt Capacity Table
• Bolt Hole Sizes
• Bolt Spacing Requirements
• Steel Fy and Fu Reference
• Bolt Grades and Strength
• Bolt Pattern Analysis
• Connection Types
• How to Verify Calculations

Disclaimer

This page is for educational and reference use only. It does not constitute professional engineering advice. All design values must be verified against AISC 360-22 Section J3.10 and the governing project specification. The site operator disclaims liability for any loss arising from the use of this information.

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