What is the section modulus of W8X58?

Sx = 52 inÃÂÃÂ³, Zx = 59.8 inÃÂÃÂ³.

What steel grade is standard for W8X58?

ASTM A992 (Fy = 50 ksi, Fu = 65 ksi) for W-shapes.

What is the moment of inertia of W8X58?

Ix = 228 inÃÂ¢ÃÂÃÂ´, Iy = 75.1 inÃÂ¢ÃÂÃÂ´.

W8X58 Steel Beam — Section Properties

Dimensions

Property	Value	Unit
Depth (d)	8.75	in (222.3 mm)
Flange Width (bf)	8.22	in (208.8 mm)
Flange Thickness (tf)	0.81	in
Web Thickness (tw)	0.51	in
Area (A)	17.10	in² (110.3 cmÃÂÃÂ²)
Weight	58	lb/ft (86 kg/m)

Elastic Section Properties

Property	Strong Axis (X-X)	Weak Axis (Y-Y)	Unit
Moment of Inertia (I)	228	75.10	in⁴
Elastic Section Modulus (S)	52	18.30	in³
Plastic Section Modulus (Z)	59.80	27.90	in³
Radius of Gyration (r)	3.65	2.10	in

Torsional Properties

Property	Value	Unit
Torsional Constant (J)	3.33	in⁴
Warping Constant (Cw)	1,180	in⁶
Distance Between Flange Centroids (ho)	7.94	in
Effective Radius (rts)	2.39	in

Section Profile Summary

Hot-rolled W-shape with Sx = 52 in³. The section is a practical choice for floor beams, roof members, and column applications in standard framing.

At 8.75" deep, this is a compact section a practical choice for joists, mezzanine framing, equipment support beams, and architectural features where depth control matters.

Key Design Checks (AISC 360)

Check	Formula	This Section
Plastic moment	Mp = Zx × Fy	2,990 kip-in
Deflection	Δ = 5wLÃÂ¢ÃÂÃÂ´/(384EIx)	Use Ix = 228 in⁴
Torsion	St. Venant = GJ/L	J = 3.33 in⁴
Column buckling	KL/r ÃÂ¢ÃÂÃÂ Fcr	r_x = 3.65 in

Design Notes

Compactness: Most W-shapes in ASTM A992 satisfy the compact limits in AISC 360 Table B4.1b for flexure (ÃÂÃÂ» ÃÂ¢ÃÂÃÂ¤ ÃÂÃÂ»p). This allows full plastic moment Mp development before local buckling occurs.
Flange local buckling (FLB): The flange slenderness ratio bf/2tf is compared against ÃÂÃÂ»pf = 0.38ÃÂ¢ÃÂÃÂ(E/Fy) ÃÂ¢ÃÂÃÂ 9.15 for compact sections.
Web local buckling (WLB): h/tw is checked against ÃÂÃÂ»pw = 3.76ÃÂ¢ÃÂÃÂ(E/Fy) ÃÂ¢ÃÂÃÂ 90.5 for flexure, and a more restrictive limit for uniform compression.
Lateral-torsional buckling (LTB): Lp ÃÂ¢ÃÂÃÂ 89.0 in (plastic limit). For unbraced lengths ÃÂ¢ÃÂÃÂ¤ Lp, the full plastic moment is available. Between Lp and Lr, linear interpolation per AISC 360 Eq. F2-2 applies.

Verification (AISC 360): 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: Roof beam (flat roof) — w8x58

Scenario: Flat roof beam with mechanical unit allowance — drainage slope not included. Simply supported wide flange, 17 ft span, 6 ft tributary width. Service loads: 25 psf dead + 20 psf live (270 plf total).

Given:

Span L = 17 ft (204 in)
Total service load w = 270 plf
Live load portion w_L = 120 plf
Section w8x58: Ix = 228 in⁴, Sx = 52 in³, Zx = 59.8 in³
Steel: ASTM A992, Fy = 50 ksi, E = 29,000 ksi
Design moment strength: φMn = 0.9 × Zx × Fy = 224 kip-ft

Step 1 — Live load deflection check:

Δ_LL = 5 w_L LÃÂ¢ÃÂÃÂ´ / (384 E Ix)

Δ_LL = 5 × (120/12) × (204)ÃÂ¢ÃÂÃÂ´ / (384 × 29,000,000 × 228)

Δ_LL = 0.03 in

Step 2 — Allowable deflection (IBC Table 1604.3, L/240):

Δ_allow = L / 240 = 204 / 240 = 0.85 in

Step 3 — Dead + live deflection:

Δ_total = 0.08 in

Step 4 — Design check:

ÃÂ¢ÃÂÃÂ Live load deflection is within the L/240 limit.

The required flexural strength at ultimate is approximately w_u LÃÂÃÂ²/8. With factored loads 1.2D + 1.6L, verify φMn = 224 kip-ft is adequate per AISC 360 Chapter F. Also check shear capacity (φVn = 0.6 Fy Aw × 0.9) and bearing at supports.

Related Resources

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 AISC 360 Manual and mill certificates before design. Results are PRELIMINARY — NOT FOR CONSTRUCTION.