Canadian Bolt Bearing and Tearout — Design per CSA S16-19 Clauses 13.11-13.12

Complete reference for bolt bearing and tearout resistance per CSA S16-19. Covers Br bearing resistance formula, tearout limit state at end holes, combined checks, and a step-by-step worked example for 350W gusset plate with A325M bolts.

Quick access: CSA bolt capacity → | Bolt spacing → | Bolted connection calculator →

CSA S16 Bearing Resistance

Per CSA S16-19 Clause 13.11.2(a), the bearing resistance of the connected part (not the bolt) at a hole is:

Br = 3.0 × phi_br × t × d_hole × Fu

Where:

• phi_br = 0.80 (resistance factor for bearing)
• t = thickness of the connected part (mm)
• d_hole = hole diameter (mm)
• Fu = tensile strength of the connected part (MPa)

Bearing Resistance Table — 350W Plates (Fu = 450 MPa)

For standard holes (d_hole = bolt dia + 2 mm for d ≤ 24 mm, bolt dia + 3 mm for d ≥ 27 mm):

Comparison with Bolt Shear Capacity

For A325M bolts (Vr AA — threads intercepted):

In all typical cases with 350W plates (Fu = 450 MPa) and A325M bolts, bolt shear governs over bearing for plate thickness ≥ 8 mm. For plates thinner than 8 mm or with lower-strength steel (300W, Fu = 440 MPa), bearing resistance may govern.

Tearout Resistance at End Holes

Per CSA S16 Clause 13.11.2(b), where the bolt centre is less than 1.5 × d_hole from the free edge:

Br_tearout = phi_br × t × e × Fu

Where e = edge distance measured from centre of hole to edge of plate in the direction of applied load. The tearout limit governs when edge distance is small.

End Distance Effect on Capacity

For M20 bolts in 10 mm 350W plate (Fu = 450 MPa):

Note: Tearout governs for all edge distances up to the point where the full bearing resistance (3.0 factor) is developed. The tearout formula uses e directly (no factor of 3.0), making it a limiting condition for end bolts.

Edge Distance Requirements

Per CSA S16-19 Table 3 (see also bolt spacing reference), minimum edge distances:

For design, the minimum edge distance used in tearout calculations is the actual distance to the edge, not the minimum code distance. If the actual edge distance exceeds 1.5 × d_hole, the full bearing resistance (3.0 factor) applies.

Combined Bearing and Tearout

The capacity per hole is the lesser of:

1. Bearing capacity: Br_bearing = 3.0 × phi_br × t × d_hole × Fu
2. Tearout capacity: Br_tearout = phi_br × t × e × Fu
3. Bolt shear: Vr (from bolt capacity table)

Net Section Fracture

After bearing and tearout are verified, the net section of the connected parts must also be checked per CSA S16 Clause 13.2:

Tr_net = phi_u × An × Fu

Where An = net area (gross area minus hole area) for tension members.

Worked Example — Gusset Plate Connection

Given: 12 mm thick 350W gusset plate (Fu = 450 MPa). Connected by 4 rows of M20 A325M bolts in standard holes (22 mm dia). Edge distance = 35 mm (sheared edge). Bolt spacing = 70 mm. Factored load Cf = 600 kN (axial tension).

Step 1 — Bolt Shear Capacity (AA — threads intercepted): Vr per M20 A325M AA = 81.3 kN 4 bolts: total Vr = 4 × 81.3 = 325.2 kN Bolt shear governs if Vf ≤ 325.2? Cf = 600 kN — need more bolts.

Try 8 bolts (2 rows of 4): Vr = 8 × 81.3 = 650.4 kN ≥ 600 kN. OK.

Step 2 — Bearing Resistance: Br = 3.0 × 0.80 × 12 × 22 × 450 / 1000 = 285.1 kN per bolt Easily satisfies 600/8 = 75 kN per bolt. OK.

Step 3 — Tearout at End Holes: Br_tearout = phi_br × t × e × Fu = 0.80 × 12 × 35 × 450 / 1000 = 151.2 kN per end bolt Interior bolts: tearout is not an issue (edge distance > 1.5 × d_hole from the loaded direction)

Step 4 — Net Section Fracture: Plate gross width = 70×3 + 2×35 = 280 mm (3 spaces at 70 mm, plus edge distances) Net width = 280 - 2 × 22 = 236 mm (two holes in cross-section) An = 236 × 12 = 2,832 mm^2 Tr = phi_u × An × Fu = 0.75 × 2,832 × 450 / 1000 = 956 kN ≥ 600 kN. OK.

Result: 8-M20 A325M bolts in 12 mm 350W gusset plate with 35 mm edge distance. All checks passed.

Block Shear

Block shear per CSA S16 Clause 13.2:

Tr_block = phi_u × (Atn × Fu + 0.60 × Avn × Fu) ≤ phi × (Atg × Fy + 0.60 × Avg × Fy)

For the gusset plate above, the block shear path would be checked for the connected end. For a typical bolt group (8 bolts in 4 rows): the net tension area along the bolt row and net shear area along the bolt lines are combined with the appropriate resistance factors.

Frequently Asked Questions

What is the bearing resistance of a 10 mm 350W plate with M20 bolts? Br = 3.0 × 0.80 × 10 × 22 × 450 / 1000 = 237.6 kN per bolt. Since M20 A325M AA bolt shear is 81.3 kN, bearing does not govern for any practical plate thickness. The bearing resistance only governs when the plate is very thin (t < 8 mm) or uses low-strength steel.

When does tearout govern over bearing in CSA S16? Tearout governs when edge distance e is small. The transition occurs at: e = 3.0 × d_hole. For M20 with 22 mm hole: e = 66 mm. For edge distances less than 66 mm, tearout resistance (phi × t × e × Fu) is less than bearing resistance (3.0 × phi × t × d_hole × Fu). For e ≥ 66 mm, the full bearing resistance applies.

How is net section fracture calculated per CSA S16? Tr_net = phi_u × An × Fu where phi_u = 0.75. An = gross area minus area of bolt holes. For staggered bolt patterns, a chain calculation along the critical path is required per Clause 13.2(a)(ii): An = t × [w - sum(d_hole) + sum(s^2/(4g))] where s = stagger spacing and g = gauge distance.

What is the minimum edge distance for M24 bolts per CSA S16? Per CSA S16 Table 3, the minimum edge distance for M24 bolts is 39 mm for sheared edges and 32 mm for rolled or flame-cut edges. These distances ensure adequate tearout capacity and prevent edge splitting during installation. For connections with high shear per bolt, edge distances should be increased above the minimum to maximise tearout resistance.

Related Pages

• CSA Bolt Capacity — A325M & A490M Tables
• CSA S16 Bolt Spacing & Edge Distance
• CSA Bolt Pretension
• Canadian Steel Properties — G40.21 Fy & Fu
• Bolt Group Capacity — Eccentric Load
• Bolted Connection Calculator
• All Canadian References

This page is for educational reference. Bearing and tearout per CSA S16-19 Clause 13.11-13.12. Verify hole sizes and edge distances against project drawings. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.

Design Resources

Calculator tools

• Bolt Torque Calculator
• Bolted Connection Calculator
• Splice Connection Calculator
• Steel Bolted Connection Calculator

Design guides

• Bolt Torque Worked Example
• Bolted Connection Checklist
• Bolted Connection Worked Example
• AISC Shear Tab Example
• EN 1993-1-8 Bolted Connection Worked Example