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.
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.
Example: 3/4" bolt, standard hole (13/16"), edge distance Le = 1.25": Lc = 1.25 - 0.406 = 0.844 in. Interior bolt at 3" spacing: Lc = 3.0 - 0.8125 = 2.1875 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: 0.752.40.750.37558 = 29.3 kips. Tearout: 0.751.20.8440.37558 = 16.5 kips. Governs: tearout = 16.5 kips.
Interior bolts (2): Lc = 3.0 - 0.8125 = 2.1875 in. Bearing: 29.3 kips. Tearout: 0.751.22.18750.37558 = 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.
Bearing/tearout for oversize and slotted holes
Larger hole diameters increase the hole deduction and reduce Lc, making tearout more likely to govern.
| Hole Type | dh for 3/4" bolt | Lc (end, Le=1.25") | Lc (interior, s=3") |
|---|---|---|---|
| Standard | 13/16" (0.813") | 0.844" | 2.188" |
| Oversize | 15/16" (0.938") | 0.781" | 2.063" |
| Short-slot (width) | 13/16" (0.813") | 0.844" | 2.188" |
Multi-code comparison
AS 4100-2020 Clause 9.2.2.4 uses Vb = 3.2dftp*fup for bearing per bolt. Edge tearout is controlled primarily through minimum edge distance requirements.
EN 1993-1-8 integrates bearing and tearout into a single equation: Fb,Rd = (k1alpha_bfudt)/gamma_M2, where alpha_b = min(alpha_d, fub/fu, 1.0) and alpha_d depends on edge distance and spacing ratios.
Common mistakes
Not checking each bolt individually. End bolts have shorter Lc values and lower tearout capacities than interior bolts.
Using bolt diameter instead of hole diameter for Lc. Clear distance is from the hole edge, not the bolt edge.
Confusing edge distance with clear distance. Edge distance Le is from bolt center to plate edge. Clear distance Lc = Le - dh/2.
Forgetting to check both plates. In a lap splice, both plates must be checked. The thinner plate or shorter edge distance governs.
Applying the 3.0 factor universally. The 3.0dt*Fu formula is only valid when deformation is not a concern. Most connections use the 2.4 factor.
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.
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.
Run this calculation
Related references
- Bolt Capacity Table
- Bolt Hole Sizes
- Bolt Spacing Requirements
- Steel Fy and Fu Reference
- 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.