--------------- | ------------------: | :-----------: | --------------------------------------- | | 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)

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 per CSA S16 Clause 13.12

Problem: Select A325 bolts (threads included) for a bracket connection with factored shear Vf = 350 kN and tension Tf = 120 kN. Use 3/4" bolts in 20 mm CSA G40.21 350W plate. Connection is bearing-type (threads in shear plane). Verify bolt spacing, edge distance, and combined shear-tension interaction per CSA S16:24.

Step 1 — Shear Capacity per CSA S16 Clause 13.12.1.2: For 3/4" A325 (threads included): Vr = 0.60 × φ_b × Ab × fu_b × 0.70 / φ_b... No, per CSA S16 Clause 13.12.1.2, factored shear resistance: Vr = 0.60 × φ_b × m × Ab × fu_b where m = 1 for single shear, φ_b = 0.80. Ab = π × (19.1/2)² = 286.5 mm². fu_b = 830 MPa. Vr = 0.60 × 0.80 × 1 × 286.5 × 830 / 1000 = 114.2 kN (threads excluded from shear plane). For threads included (0.70 factor per Clause 13.12.1.2): Vr_threads = 0.70 × 114.2 = 79.9 kN. Alternatively, from AISC Table 7-1 equivalent: 88.3 kN per bolt (accounts for tensile area At = 285 mm²). Using CSA S16 direct calculation with At: Vr = 0.60 × 0.80 × 285 × 830 / 1000 = 113.5 kN × 0.70 = 79.5 kN.

Step 2 — Number of Bolts for Shear (CSA S16 Clause 13.12.1.1): n_shear = Vf / Vr = 350 / 79.5 = 4.40 → use 5 bolts minimum.

Step 3 — Tension Capacity per CSA S16 Clause 13.12.1.3: Tr = 0.75 × φ_b × Ab × fu_b = 0.75 × 0.80 × 286.5 × 830 / 1000 = 142.7 kN per bolt. n_tension = Tf / Tr = 120 / 142.7 = 0.84 → 1 bolt sufficient for tension. Use 5 bolts for shear.

Step 4 — Combined Shear-Tension per CSA S16 Clause 13.12.1.4: For combined loading: (Vf / Vr)² + (Tf / Tr)² ≤ 1.0. Per bolt: Vf_per = 350/5 = 70 kN, Tf_per = 120/5 = 24 kN. (70/79.5)² + (24/142.7)² = 0.775 + 0.028 = 0.803 ≤ 1.0. OK.

Step 5 — Bolt Spacing per CSA S16 Clause 22.3.2: Minimum centre-to-centre spacing = 2.7 × d = 2.7 × 19.1 = 51.6 mm (use 55 mm minimum). Preferred = 3 × d = 57 mm. Use 75 mm spacing. Minimum edge distance per CSA S16 Table 6: for 3/4" bolt = 29 mm (sheared edge) or 24 mm (rolled edge). Use 35 mm edge distance.

Step 6 — Bearing Resistance per CSA S16 Clause 13.12.1.1: Br = 3 × φ_br × t × d × fu where φ_br = 0.80. Plate 350W: fu = 450 MPa, t = 20 mm. Br = 3 × 0.80 × 20 × 19.1 × 450 / 1000 = 412.6 kN per bolt interior. For edge bolts (Le = 35 mm): Br = Le × φ_br × t × fu = 35 × 0.80 × 20 × 450 / 1000 = 252 kN ≥ Vr (79.5 kN). Bearing is adequate.

Result: Use 5 × 3/4" A325 bolts at 75 mm centres. Edge distance 35 mm. Combined shear-tension ratio 0.803 < 1.0. All checks per CSA S16:24 Clauses 13.12.1 and 22.3 satisfied.

Design Resources

• Canadian Steel Grades
• Canadian Steel Properties
• Canadian CSA Bolt Capacity
• CSA S16 Beam Design
• All Canadian References

Design Applications

Common Design Scenarios

This reference covers structural design scenarios commonly encountered in structural steel design practice:

• Strength verification: Check member or connection capacity against factored loads per the applicable design code
• Serviceability checks: Verify deflections, vibrations, and other serviceability criteria
• Code compliance: Ensure design meets all provisions of the governing standard
• Connection detailing: Verify weld sizes, bolt quantities, and edge distances

Related Design Considerations

• System behavior: consider the interaction between members and connections
• Load paths: verify that forces can be transferred through the structure to the foundations
• Constructability: check that the design can be fabricated and erected practically
• Cost optimization: evaluate alternative sections or connection types for economy

Worked Example

Problem: Verify a typical steel member for the following conditions:

Typical span: 6.0 m | Load: service loads per applicable code | Section: common section in this category

Design Check:

1. Determine governing load combination (LRFD or ASD per applicable code)
2. Calculate maximum internal forces (moment, shear, axial)
3. Compute nominal capacity per code provisions
4. Apply resistance/safety factors
5. Verify interaction if combined forces exist

Result: Use the results from the Steel Calculator tool to verify design adequacy.

Frequently Asked Questions

What Canadian Standard governs structural steel design?

CSA S16:24 (Design of Steel Structures) is the primary standard for structural steel design in Canada. It covers member design, connections, serviceability, and seismic provisions using limit states design with resistance factors (φ). Companion standards include CSA G40.21 for structural steel grades, CSA W59 for welding, and CSA S136 for cold-formed steel. The standard references ASTM specifications for bolts (F3125) and anchors.

What steel grades are commonly used in Canadian construction?

Per CSA G40.21, the most common structural steel grades are 350W (fy = 350 MPa), 350WT (notch-tough), and 350AT (atmospheric corrosion-resistant). Grade 300W is also used for lighter applications. CSA G40.21 grades are similar to ASTM A572 Grade 50 and A992. Weathering steel (350AT) is popular for exposed structures and bridges. Hollow structural sections follow CSA G40.21 Class C (cold-formed) or Class H (hot-formed).

How does CSA S16 compare to AISC 360 for structural steel design?

CSA S16:24 and AISC 360-22 both use limit states design but differ in several areas. CSA S16 uses φ = 0.90 for steel in tension and flexure (AISC: φ = 0.90 same), φ = 0.80 for bolts (AISC: φ = 0.75), and φ = 0.67 for welds (AISC: φ = 0.75). CSA S16 has explicit provisions for Class 4 (slender) sections in Annex H. Seismic design (Clause 27) requires capacity design for ductile frames. The Canadian code references unique steel grades per CSA G40.21 rather than ASTM A992/A572.

Frequently Asked Questions

What bolt grades are used in Canadian steel construction? CSA S16:24 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 S16:24 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 S16:24. This information does not constitute professional engineering advice. Always consult a qualified structural engineer.