Canadian Bolt Grades — CSA S16 & CSA G40.20 Guide
Bolt grades for structural steel construction in Canada follow ASTM A325 (now ASTM F3125 Grade A325) and ASTM A490 (Grade A490) as adopted by CSA S16:19 Clause 22.3. Canadian practice closely follows US bolt classifications but with Canadian-specific material standards and nominal bolt diameters in imperial units.
Bolt Grade Mechanical Properties
| Grade | Diameter Range (in) | Min fub (MPa) | Application |
|---|---|---|---|
| ASTM A325 (Type 1) | 1/2 — 1 | 830 | Medium-carbon steel, bolted connections |
| ASTM A325 (Type 1) | 1-1/8 — 1-1/2 | 725 | Medium-carbon steel, larger diameters |
| ASTM A490 (Type 1) | 1/2 — 1-1/2 | 1040 | Alloy steel, higher strength |
| ASTM F3125 A325 | 1/2 — 1-1/2 | 830 | Replacement spec for A325 |
| ASTM F3125 A490 | 1/2 — 1-1/2 | 1040 | Replacement spec for A490 |
Bolt Grade Applications
A325 (Grade 8.8 equivalent): The standard bolt grade for most structural connections per CSA S16. Used for bearing-type connections (threads included or excluded) and slip-critical connections. Readily available, cost-effective, and suitable for galvanizing.
A490 (Grade 10.9 equivalent): Higher strength bolts used where space or bolt count is constrained. Not recommended for galvanizing due to hydrogen embrittlement risk. Must be installed with hardened washers per CSA S16 Clause 22.3.5.
CSA S16 Design Capacities — Factored (phi = 0.80)
| Bolt Size | Area (mm²) | A325 — Shear Threads In (kN) | A325 — Shear Threads Out (kN) | A325 — Tension (kN) |
|---|---|---|---|---|
| 3/4" (19.1 mm) | 285 | 88.3 | 118.2 | 141.4 |
| 7/8" (22.2 mm) | 387 | 119.8 | 160.5 | 192.0 |
| 1" (25.4 mm) | 506 | 156.9 | 210.0 | 251.4 |
| 1-1/8" (28.6 mm) | 643 | 199.4 | 186.7 | 279.8 |
| 1-1/4" (31.8 mm) | 794 | 246.1 | 230.2 | 345.4 |
Note: A325 fu = 830 MPa for bolts ≤ 1", 725 MPa for > 1". Shear threads out uses body area Ab; shear threads in uses tensile area At.
Worked Example: Bolt Selection
Problem: Select the number of 3/4" A325 bolts (threads included) required for a bracket connection with factored shear Vf* = 350 kN per CSA S16.
Solution:
- From table: phi Vfn (3/4" A325, threads included) = 88.3 kN per bolt
- Number required: n = 350 / 88.3 = 3.96 → use 4 bolts
- Check spacing: 4 bolts at 3" spacing = 9" bolt group length — OK for typical connection
Design Resources
- Canadian Steel Grades
- Canadian Steel Properties
- Canadian CSA Bolt Capacity
- CSA S16 Beam Design
- All Canadian References
Frequently Asked Questions
What bolt grades are used in Canadian steel construction? CSA S16:19 references ASTM A325 and A490 bolts (now consolidated under ASTM F3125 Grades A325 and A490). Grade A325 (fub = 830 MPa for diameters ≤ 1") is the standard for most structural connections. Grade A490 (fub = 1040 MPa) is used where higher strength is needed but is not suitable for all environments.
What is the capacity factor for bolts per CSA S16? CSA S16:19 Clause 13.11 specifies phi = 0.80 for bolt shear and tension. This applies to both A325 and A490 bolts. The factored resistance is phi times the nominal resistance per bolt.
How does CSA S16 handle slip-critical connections? Per CSA S16 Clause 22.3.6, slip-critical connections are required for connections subject to fatigue, reversal of load, or where slip would cause unacceptable deformation. The slip resistance is determined by the bolt pretension (70% of minimum tensile strength per turn-of-nut method) multiplied by the slip coefficient for the faying surface condition (typically 0.33 for clean mill scale, 0.50 for blast-cleaned).
Educational reference only. Verify all values against the current edition of CSA S16:19. This information does not constitute professional engineering advice. Always consult a qualified structural engineer.