W-Shapes — G40.21 350W Steel

Canadian W-shapes are manufactured to ASTM A992/A992M and CSA G40.21 Grade 350W. They are the primary beam sections in Canadian steel construction. Dimensions are metric but the designations retain imperial depth (nominal inches).

WWF Shapes — Welded Wide Flange

WWF sections are fabricated by welding three plates in Canada. Used for heavy industrial and bridge applications where rolled W-shapes are unavailable.

Grade: CSA G40.21 350A/350AT (with notch toughness for tension flange applications). WWF sections typically require CVN testing for primary tension members per CSA S16 Clause 27.

HSS — Hollow Structural Sections

Canadian HSS are manufactured to CSA G40.21 Grade 350W Class C (cold-formed) or Class H (hot-formed). Common sizes for beams, columns, and trusses:

For Canadian HSS beam design, note that CSA S16 Table 2 classifies HSS walls differently than W-shape flanges. HSS walls under flexure are Class 1 if b/t ≤ 420/sqrt(F_y)^2, Class 2 if ≤ 525/sqrt(F_y), and Class 3 if ≤ 670/sqrt(F_y). For 350W, the Class 3 limit is b/t ≤ 35.8. Check each HSS size against these limits.

Worked Example — Canadian Floor Beam Selection

Problem: Select a W-shape for a Canadian office floor beam spanning 8.0 m at 3.5 m centres. Live load 4.8 kPa (office per NBCC Table 4.1.5.3). Dead load 3.5 kPa (130 mm concrete slab on steel deck). Grade 350W steel.

Step 1 — Loads:

w_D = 3.5 × 3.5 = 12.25 kN/m (add 0.5 kN/m for self-weight, total 12.75). w_L = 4.8 × 3.5 = 16.80 kN/m.

ULS: w_f = 1.25 × 12.75 + 1.5 × 16.80 = 15.94 + 25.20 = 41.14 kN/m.

Step 2 — Moment and Shear:

M_f = 41.14 × 8.0² / 8 = 329.1 kN·m. V_f = 41.14 × 8.0 / 2 = 164.6 kN.

Step 3 — Required Section Modulus:

Z_req = M_f / (phi × F_y) = 329.1 × 10⁶ / (0.90 × 350) = 1,044 × 10³ mm³.

Try W460x74 (Z_x = 1,720 × 10³ mm³): phi × M_p = 0.90 × 1,720 × 350 × 10³ / 10⁶ = 541.8 kN·m. M_f / (phi × M_p) = 329.1 / 541.8 = 0.607. OK.

Step 4 — Deflection:

delta_LL = 5 × 16.80 × 8000⁴ / (384 × 200,000 × 333 × 10⁶) = 5 × 16.80 × 4.096 × 10¹⁵ / (384 × 200,000 × 333 × 10⁶) = 3.44 × 10¹⁷ / 2.558 × 10¹⁶ = 13.5 mm.

L/360 = 8000/360 = 22.2 mm. OK (61% utilisation).

Selected: W460x74 Grade 350W, with intermediate bracing at 2.67 m spacing for LTB control.

Beam Depth Selection � Canadian Rules of Thumb

For preliminary steel beam sizing in Canadian practice, the following span-to-depth ratios provide reasonable starting points (Grade 350W steel, typical office/live loads):

For a 10 m floor beam: depth range = 10,000 / 22 to 10,000 / 18 = 455 to 555 mm. Start with W460 or W530 sections.

Deflection check: Canadian practice per NBCC Table 4.1.3.4 limits live load deflection to L/360 for floors and L/240 for roof beams supporting non-plaster ceilings. Dead load deflection should be accounted for by cambering if it exceeds 12-15 mm.

Vibration: For Canadian office floors, the CSA S16 Commentary (Clause 7.4) recommends a minimum natural frequency of 5 Hz for walking excitation. As a quick check: f_n � 18 / sqrt(delta_LL in mm). For delta_LL = 13.5 mm: f_n = 18 / sqrt(13.5) = 4.9 Hz � marginal. Increase depth to W530 to push f_n above 5 Hz.

WWF Fabrication � Quality Requirements

Welded Wide Flange (WWF) sections are fabricated per CSA W59 and CSA S16 Clause 24. Key requirements for Canadian WWF beams:

Material: Web and flange plates to CSA G40.21 Grade 350A with Charpy V-notch (CVN) testing at the minimum design temperature when the tension flange is a primary tension member (CSA S16 Clause 27).

Weld type: Full-penetration groove welds or partial-penetration groove welds with fillet reinforcement. For dynamically loaded members, full-penetration welds are mandatory at the flange-to-web junction per CSA S16 Table 3.

Weld access hole: Per CSA W59, weld access holes (rat holes) at flange splices must have a minimum radius of 25 mm with smooth transitions � no sharp notches that could initiate brittle fracture in cold-climate applications.

Inspection: Full UT (ultrasonic testing) of all T-joint groove welds for primary tension members. Visual inspection (VT) for all welds per CSA W59 acceptance criteria.

Dimensional tolerances: Per CSA G40.21 tolerances: web off-centre +/- 3 mm, camber +/- L/1000 (max 10 mm), flange tilt +/- 2 mm. Tighter tolerances than rolled sections because each WWF is piece-fabricated.

Section properties: WWF sections are typically deeper and heavier than rolled W-shapes of equivalent weight, since the welded fabrication is optimised for stiffness. I_x can be 20-40% higher than an equivalent-weight rolled W-shape due to the ability to increase depth without increasing flange thickness proportionally.

Related Pages

• CSA S16 Beam Design — Worked Example
• Canadian Steel Grades — G40.21 350W Reference
• CSA S16 Column Design — Worked Example
• CSA S16 Load Combinations — NBCC ULS & SLS
• Canadian HSS Connections — CSA S16
• CSA S16 Bolt Capacity — Bolt Tables
• Canada Steel Properties — fy & fu Values
• Beam Capacity Calculator — Free Tool

Educational reference only. Verify section properties against current CISC Handbook (12th Ed.) and ASTM A6/A6M. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent P.Eng. verification.