Bolt Bearing & Tear-Out Design — Formulas and Limits per AISC 360, AS 4100, EN 1993, CSA S16

Complete bolt bearing and tear-out design reference covering all four major structural steel codes: AISC 360-22, AS 4100-2020, EN 1993-1-8, and CSA S16:24. Includes side-by-side formula comparison tables, edge distance requirements, bolt spacing minimums, worked examples for each code, and a free interactive calculator.

Quick navigation: Bearing vs. Tear-Out · Formula Comparison Table · AISC 360 · AS 4100 · EN 1993-1-8 · CSA S16:24 · Worked Examples · FAQ

PRELIMINARY — NOT FOR CONSTRUCTION. All results are for educational and reference use only. Must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) before use in any project.

Bearing vs. Tear-Out

What is Bolt Bearing?

Bolt bearing is a localized compressive crushing failure of the base metal immediately behind the bolt hole wall. When a bolted connection is loaded in shear, the bolt shank bears against the hole wall in the connected plies. If the plate is too thin or the applied force too high, the plate material yields in bearing, causing hole elongation and permanent deformation.

Bearing capacity is governed by:

• Bolt diameter d — larger bolts distribute force over more plate area
• Plate thickness t — doubling plate thickness doubles bearing capacity
• Plate ultimate tensile strength Fu — bearing is a fracture-governed limit state

What is Tear-Out?

Tear-out (also called edge shear-out or bolt-hole tear-out) is a shear rupture failure where the plate material between the bolt hole and the nearest free edge shears along two parallel planes. The bolt essentially "rips out" a plug of material ahead of it. Unlike bearing, which is progressive and ductile, tear-out approaches a brittle failure and must be carefully controlled.

Tear-out capacity depends on:

• Clear distance Lc — the distance from the hole edge to the free edge or adjacent hole
• Plate thickness t and ultimate tensile strength Fu — same as bearing
• Number of shear planes engaged — tear-out is a planar shear failure

Key Difference

For every bolt in a bearing-type connection, both bearing and tear-out must be checked. The governing capacity per bolt is the minimum of the two values. End bolts with small edge distances almost always have tear-out as the controlling limit state; interior bolts with standard 3d spacing almost always have bearing as the controlling limit state.

Edge Distance Requirements

Minimum edge distance requirements ensure that the plate material does not shear out during punching or drilling operations. However, these minimum values from the codes may still result in tear-out governing over bearing. For full bearing capacity, larger edge distances are recommended.

Edge Distance Minimums by Code

AISC 360 Table J3.4 Minimum Edge Distances (Standard Holes)

Bolt Spacing Minimums by Code

For interior bolts, using the minimum spacing means Lc ≈ 1.7d (AISC) to 1.8d (CSA), where bearing is the transition zone — close to or at the threshold where bearing begins to govern over tear-out. Using 3d spacing provides Lc ≈ 2.2d, giving a comfortable margin where bearing governs.

Formula Comparison Table

The four major structural steel codes use fundamentally similar mechanics for bearing and tear-out but differ in coefficients, resistance factors, and the treatment of deformation.

AISC 360-22

AISC 360-22 Section J3.10 provides four equations depending on whether deformation at the bolt hole at service load is a design consideration.

Bearing (Eq. J3-6a, J3-6c)

Deformation IS a design consideration (building structures — standard case):

[ \phi R_n = 0.75 \times 2.4 \times d \times t \times F_u ]

Deformation is NOT a design consideration (temporary structures, acceptable hole elongation):

[ \phi R_n = 0.75 \times 3.0 \times d \times t \times F_u ]

Tear-Out (Eq. J3-6b, J3-6d)

Deformation IS a design consideration:

[ \phi R_n = 0.75 \times 1.2 \times L_c \times t \times F_u ]

Deformation is NOT a design consideration:

[ \phi R_n = 0.75 \times 1.5 \times L_c \times t \times F_u ]

Key Parameters

• φ = 0.75 for all bearing and tear-out limit states (LRFD)
• d = nominal bolt diameter (in)
• t = thickness of the connected material (in)
• Fu = specified minimum tensile strength of the connected material (ksi)
• Lc = clear distance (in) = Le - dh/2 for end bolts; Lc = s - dh for interior bolts
• dh = hole diameter (standard: d + 1/16 in)

Critical Transition

Tear-out governs when Lc < 2d. For a 3/4" bolt (d = 0.75), tear-out governs when Lc < 1.50 in. At the AISC minimum end distance for rolled edge (Le = 1.0 in), Lc = 1.0 - 0.406 = 0.594 in, and tear-out is only ~53% of bearing capacity.

AS 4100-2020

AS 4100-2020 Clause 9.3.2.4 uses a slightly different approach: bearing capacity is expressed as a function of the bearing coefficient and edge/end distance effects are handled through the minimum edge distance table and an effective bearing area.

Bearing (Clause 9.3.2.4)

[ \phi Vb = 0.80 \times 3.2 \times d_f \times t_p \times f{up} ]

Tear-Out

AS 4100 controls tear-out primarily through minimum edge distance requirements in Table 9.3.2. The code does not provide a separate tear-out strength equation; instead, the minimum edge distances are set conservatively to ensure bearing (not tear-out) governs for standard connections.

When edge distances are below table minimums, a reduced effective bearing area ae must be used:

[ \phi Vb = 0.80 \times a_e \times t_p \times f{up} ]

Where ae = Le - dh/2 for end bolts and ae = s - dh for interior bolts.

Key Parameters

• φ = 0.80 (for bearing on structural members and plates)
• φ = 0.60 (for ply in bearing in lap connections per Clause 9.3.2.5)
• df = nominal bolt diameter (mm)
• tp = thickness of the connected ply (mm)
• fup = ultimate tensile strength of the ply (MPa)

Bearing Coefficient Comparison

AS 4100's coefficient of 3.2 is higher than AISC's 2.4 (deformation concern) — it corresponds more closely to AISC's "deformation not a concern" coefficient of 3.0. Australian practice generally accepts slightly larger hole elongation at service loads.

EN 1993-1-8

EN 1993-1-8 Table 3.4 integrates bearing and tear-out into a single unified equation using two dimensionless factors: α_b (for end distance and bolt spacing in the direction of load) and k₁ (for edge distance perpendicular to the load).

Unified Bearing/Tear-Out Equation (Table 3.4)

[ F*{b,Rd} = \frac{k_1 \times \alpha_b \times f_u \times d \times t}{\gamma*{M2}} ]

Parameters

• γ_M2 = 1.25 (partial safety factor for bolted connections in bearing)
• d = bolt diameter (mm)
• t = plate thickness (mm)
• fu = ultimate tensile strength of the plate (MPa)

α_b — End Distance Factor

For end bolts (in direction of load transfer):

[ \alpha_d = \frac{e_1}{3 \times d_0} ]

For inner bolts:

[ \alpha_d = \frac{p_1}{3 \times d_0} - \frac{1}{4} ]

Then α_b = min(α_d, fub/fu, 1.0), where fub is the bolt ultimate tensile strength and fu is the plate ultimate tensile strength.

k₁ — Edge Distance Factor

For edge bolts (perpendicular to load direction):

[ k_1 = \min\left(2.8 \times \frac{e_2}{d_0} - 1.7, \quad 2.5\right) ]

For inner bolts:

[ k_1 = \min\left(1.4 \times \frac{p_2}{d_0} - 1.7, \quad 2.5\right) ]

How EN 1993-1-8 Handles Tear-Out

When the edge distance e₁ is small, αb becomes small, reducing F{b,Rd}. This is the tear-out-limited case. When e₁ is large enough, α_b reaches its cap of 1.0 (or fub/fu), and bearing governs. The transition edge distance for α_b = 1.0 is e₁ = 3 × d₀ (approximately 3.2d for standard holes).

This means EN 1993-1-8 implicitly requires larger edge distances to develop full bearing capacity compared to AISC (where Lc = 2d triggers bearing governing). The Eurocode approach is more conservative on edge distances.

CSA S16:24

CSA S16:24 Clause 13.12.1.2 follows an approach similar to AISC but with different coefficients and resistance factors.

Bearing (Clause 13.12.1.2)

[ Br = \phi{br} \times 3.0 \times t \times d \times F_u ]

Tear-Out

[ Br = \phi{br} \times t \times L_e \times F_u ]

Where Le = clear distance from hole edge to adjacent edge or hole (equivalent to Lc in AISC): Le = edge distance - dh/2 for end bolts, or spacing - dh for interior bolts.

Key Parameters

• φ_br = 0.67 (bearing resistance factor for standard holes in bearing-type connections)
• φ_br = 0.60 (for oversize and slotted holes)
• t = thickness of the connected material (mm)
• d = bolt diameter (mm)
• Fu = specified minimum tensile strength of the connected material (MPa)

Comparison to AISC

CSA S16:24 uses a bearing coefficient of 3.0 (same as AISC's "deformation not a concern"), but combines it with a lower resistance factor φ_br = 0.67 vs. AISC's φ = 0.75. For tear-out, CSA uses a coefficient of 1.0 (vs. AISC's 1.2 for deformation concern), also with the lower φ_br. End result: CSA S16:24 typically yields slightly lower design capacities for the same bolt and plate configuration — roughly 5-10% more conservative than AISC for bearing and 10-15% more conservative for tear-out.

Cross-Code Capacity Comparison

The table below compares design capacities for a 3/4" bolt in a 3/8" A36 plate (Fu = 58 ksi / 400 MPa), Le = 1.25 in / 32 mm, spacing = 3 in / 76 mm, standard holes.

Note: Imperial/metric conversions are approximate. Actual values depend on exact material grades and hole sizes. Run the calculator for your specific configuration.

Worked Examples

Example 1 — AISC 360: 4-Bolt Lap Splice

Given: W18×50 beam web (tw = 0.355 in) spliced with two 3/8 in A36 plates (Fu = 58 ksi). Four 3/4" A325-N bolts in a single vertical line. Edge distance Le = 1.25 in at both ends. Bolt spacing s = 3 in. Standard holes.

Step 1 — Hole diameter: dh = d + 1/16 = 0.75 + 0.0625 = 0.8125 in

Step 2 — Clear distances: End bolts (2): Lc = Le - dh/2 = 1.25 - 0.406 = 0.844 in Interior bolts (2): Lc = s - dh = 3.0 - 0.8125 = 2.188 in

Step 3 — Bearing (per bolt, deformation IS a concern): φRn,bearing = 0.75 × 2.4 × 0.75 × 0.375 × 58 = 29.4 kips (same for all bolts)

Step 4 — Tear-out: End bolt: φRn,tear = 0.75 × 1.2 × 0.844 × 0.375 × 58 = 16.6 kips (tear-out governs) Interior bolt: φRn,tear = 0.75 × 1.2 × 2.188 × 0.375 × 58 = 42.9 kips (bearing governs at 29.4)

Step 5 — Total connection bearing capacity: 2 × 16.6 + 2 × 29.4 = 33.2 + 58.8 = 92.0 kips

Observation: Doubling the end edge distance to Le = 2.5 in brings Lc, end to 2.094 in and tear-out to 41.1 kips — now bearing governs for end bolts too. Total rises to 4 × 29.4 = 117.6 kips, a 28% increase.

Example 2 — EN 1993-1-8: M20 Bolts, S355 Plate

Given: M20 (d = 20 mm) Grade 8.8 bolts, t = 10 mm plate, S355 (fu = 510 MPa), e₁ = 32 mm end distance, p₁ = 75 mm spacing, e₂ = 30 mm edge distance. d₀ = 22 mm (standard clearance).

Step 1 — α_b for end bolt: α_d = e₁ / (3 × d₀) = 32 / (3 × 22) = 32 / 66 = 0.485 fub / fu = 800 / 510 = 1.57 α_b = min(0.485, 1.57, 1.0) = 0.485

Step 2 — α_b for interior bolt: α_d = p₁ / (3 × d₀) - 1/4 = 75 / 66 - 0.25 = 1.136 - 0.25 = 0.886 α_b = min(0.886, 1.57, 1.0) = 0.886

Step 3 — k₁ (edge bolts): k₁ = min(2.8 × e₂ / d₀ - 1.7, 2.5) = min(2.8 × 30/22 - 1.7, 2.5) = min(3.818 - 1.7, 2.5) = 2.12

Step 4 — Bearing capacity per bolt: End bolt: F_b,Rd = 2.12 × 0.485 × 510 × 20 × 10 / 1.25 = 84,110 N = 84.1 kN Interior bolt: F_b,Rd = 2.12 × 0.886 × 510 × 20 × 10 / 1.25 = 153,160 N = 153.2 kN

Observation: The end bolt capacity is only 55% of the interior bolt capacity. Increasing e₁ to 50 mm raises α_d to 0.758 and α_b to 0.758, bringing end bolt capacity to 131.5 kN — a 56% gain from a 56% increase in edge distance.

Example 3 — CSA S16:24: End Bolt vs. Interior Bolt

Given: 3/4" (d = 19.05 mm) A325 bolts, 10 mm A36 plate (Fu = 400 MPa), Le = 32 mm edge, s = 76 mm spacing, standard holes (dh = 20.7 mm).

Step 1 — Bearing: Br,bearing = 0.67 × 3.0 × 10 × 19.05 × 400 = 153,243 N = 153.2 kN per bolt

Step 2 — Tear-out end bolt: Le,clear = 32 - 20.7/2 = 32 - 10.35 = 21.65 mm Br,tear = 0.67 × 10 × 21.65 × 400 = 58,022 N = 58.0 kN (tear-out governs)

Step 3 — Tear-out interior bolt: Le,clear = 76 - 20.7 = 55.3 mm Br,tear = 0.67 × 10 × 55.3 × 400 = 148,204 N = 148.2 kN (bearing governs at 153.2)

Step 4 — Connection with 2 end + 2 interior: 2 × 58.0 + 2 × 148.2 = 116.0 + 296.4 = 412.4 kN

Observation: The end bolt tear-out at 58.0 kN is only 38% of interior bolt capacity (153.2 kN). This dramatic difference underscores why end edge distance is typically the most critical geometric parameter in bolted connections.

Frequently Asked Questions

What is the difference between bolt bearing and tear-out?

Bolt bearing is compressive crushing of the plate material behind the bolt hole. It is ductile — the hole progressively elongates, giving visible warning. Tear-out is a shear rupture where a block of plate material shears out from the bolt hole to the nearest edge. It has limited ductility. In design, bearing is preferred; tear-out is accepted when unavoidable at end bolts.

Which edge distance should I use — code minimum or something larger?

Use the code minimum only if you have verified that the resulting tear-out capacity is adequate for your applied loads. For most practical designs, use edge distance ≥ 1.5d for bolts up to 3/4" and ≥ 2d for larger bolts. This ensures bearing governs over tear-out and gives maximum connection efficiency.

Does the deformation concern distinction in AISC matter?

Yes. The "deformation IS a design concern" equations (2.4 and 1.2 coefficients) apply to virtually all building connections. The "not a concern" equations (3.0 and 1.5) provide 25% more capacity but allow hole elongation > 1/4" at service loads — acceptable for temporary works, some industrial structures, or where slip-critical connections prevent any hole bearing under service loads.

How do I check bearing for long-slotted holes?

AISC 360 reduces the tear-out coefficient from 1.2 to 1.0 for long-slotted holes with the slot perpendicular to the force. For slots parallel to the force, the clear distance Lc is dramatically reduced (Lc = Le - slot_length/2 for end bolts). This can make tear-out the governing limit state at edge distances that would normally develop full bearing in standard holes.

Do I need to check bearing and tear-out for slip-critical connections?

Yes. Bearing and tear-out are ultimate limit state checks that must be satisfied even for slip-critical connections. If the connection ever slips under extreme loading, the bolts go into bearing. For slip-critical connections at service loads, the slip resistance is the governing serviceability check, but bearing/tear-out must still satisfy the ultimate limit state requirement.

Is there a simple rule of thumb for when bearing governs?

For AISC 360: bearing governs when Lc > 2d. For 3/4" bolts with standard 3" spacing, Lc = 2.188 in > 1.50 in = 2d — bearing governs for interior bolts. For end bolts, Le must be ≥ 1.5 in + dh/2 ≈ 1.91 in for bearing to govern. A safe default for all codes: use Le ≥ 2d end distance and s ≥ 3d spacing.

Run This Calculation

→ Bolted Connection Calculator — full bolt group analysis with bearing, tear-out, bolt shear, and block shear per AISC 360.

→ Splice Connection Calculator — tension splice design with complete Chapter J bearing and tear-out checks.

→ Section Properties Database — look up plate Fu values and hole sizes.

Try it now: Check your bolt bearing and tear-out design with our free Bolted Connection calculator →

Related Pages

• Bolt Bearing & Tearout — AISC J3.10 Tables — AISC-only deep dive
• Bolt Shear vs. Bearing — comparing limit states
• Bolt Capacity Table — A325 & A490 — shear and tension per bolt
• Bolt Spacing & Edge Distance — all code minimums
• Bolt Hole Sizes — Standard, Oversize, Slotted
• Steel Fy & Fu — material properties for all grades
• Block Shear Rupture — AISC J4.3
• Steel Code Comparison — full multi-code comparison

Disclaimer

This page is for educational and reference use only. It does not constitute professional engineering advice. All design values must be verified against the governing design code (AISC 360-22, AS 4100-2020, EN 1993-1-8, or CSA S16:24) and the specific project specification. The site operator disclaims liability for any loss arising from the use of this information.

Design Resources

Calculator tools

• Bolted Connection Calculator
• Splice Connection Calculator
• End Plate Moment Connection Calculator
• Fin Plate Shear Connection Calculator
• Gusset Plate Calculator

Design guides

• Bolted Connection Worked Example
• Bolted Connection Checklist
• EN 1993-1-8 Bolted Connection Worked Example
• Steel Connection Calculator Guide
• AISC Shear Tab Example

Reference pages

• Bolt Grades & Strength
• Bolt Pattern Analysis
• Connection Types Explained
• Structural Steel Properties
• Weld Capacity Reference