380PFC AS/NZS 3679.1 Grade 300 — Australian Parallel Flange Channel Section Properties

380PFC is an Australian PFC (Parallel Flange Channel) per AS/NZS 3679.1 hot-rolled structural steel section. Standard Australian PFC dimensions. Verify against Liberty OneSteel / InfraBuild section catalog.

Dimensions (Metric)

Elastic Section Properties (Metric)

Torsional Properties

Section Profile Summary

Unlike doubly-symmetric sections, channel bending about the weak axis produces twist. Where weak-axis flexure is unavoidable, provide torsional restraint at close intervals or switch to a hollow section.

At 380 mm deep, this section is common for floor beams, portal frame rafters, and columns in commercial and industrial buildings.

Key Design Checks (AS 4100)

Design Notes

• Section asymmetry: The shear center lies outside the web. Loads not applied through the shear center produce torsion. Provide intermediate torsional restraints or stiffeners when the load eccentricity is significant.
• Lateral-torsional buckling: Check Cb (moment modification factor) per AS 4100 Chapter F — channels are more sensitive to load height effects than doubly-symmetric sections.
• Web crippling at supports: For channels used as beams, bearing stiffeners may be needed at concentrated load points per AS 4100 Section J10.

Verification (AS 4100): All designs using this section must be verified by a licensed Professional Engineer. Before finalizing member selection, check beam-column interaction (P-M), lateral-torsional buckling, serviceability deflections, and all connection limit states. See Engineering Disclaimer.

Worked Example: Hospital ward beam — 380pfc

Scenario: Hospital ward — strict deflection limits for medical equipment and services. Simply supported channel, 6.8 m span, 2.1 m tributary width. Service loads: 4.0 kPa dead + 3.0 kPa live (14.7 kN/m total).

Given:

• Span L = 6840 mm (6.8 m)
• Total service load w = 14.7 kN/m
• Live load portion w_L = 6.3 kN/m
• Section 380pfc: Ix = 141.2 × 10⁶ mm⁴, Sx = 743,000 mm³, Zx = 885,000 mm³
• Steel: fy = 300 MPa, E = 200,000 MPa
• Design moment resistance: φMn = 0.9 × Zx × fy = 239 kN·m

Step 1 — Live load deflection:

Δ_LL = 5 w_L L⁴ / (384 E Ix)

Δ_LL = 5 × 6.3 × (6840)⁴ / (384 × 200000 × 141,190,000)

Δ_LL = 6.4 mm

Step 2 — Deflection limit (L/360):

Δ_limit = L / 360 = 6840 / 360 = 19.0 mm

Step 3 — Dead + live deflection:

Δ_total = 14.8 mm

Step 4 — Design check:

✓ Live load deflection is within the L/360 limit.

Verify the design moment M*_Ed (from factored loads 1.35G + 1.5Q per AS 4100) does not exceed φMn = 239 kN·m. Also confirm shear resistance and bearing details at the supports.

Related Resources

• Steel Beam Capacity Calculator
• Column Capacity Calculator
• Beam Deflection Calculator
• Section Properties Calculator
• Steel Grades Reference
• Section Comparison Tool

Design Resources

• Section Properties Lookup — Compare with similar sections
• Steel Beam Sizes Reference — Standard beam dimensions

Educational reference only. Verify all section properties against the current AS 4100 Manual and mill certificates before design. Results are PRELIMINARY — NOT FOR CONSTRUCTION.