What is the section modulus of WT12X34?

Sx = 15.6 inÃÂÃÂ³, Zx = 27.9 inÃÂÃÂ³ (strong axis). Sy = 7.85 inÃÂÃÂ³, Zy = 12.3 inÃÂÃÂ³ (weak axis).

What steel grade is standard for WT12X34?

ASTM A992 (Fy = 50 ksi, Fu = 65 ksi) for WT-shapes. Verify with mill certificate.

What is the moment of inertia of WT12X34?

Ix = 137 inÃÂ¢ÃÂÃÂ´ about the strong axis and Iy = 35.2 inÃÂ¢ÃÂÃÂ´ about the weak axis. The radius of gyration is rx = 3.7 in and ry = 1.87 in.

WT12X34 Steel WT-shape — Section Properties

Dimensions

Property	Value	Unit
Depth (d)	11.9	302.3 mm
Flange Width (bf)	8.97	22.78 cm
Flange Thickness (tf)	0.585	14.9 mm
Web Thickness (tw)	0.415	10.5 mm
Area (A)	10 in²	64.5 cmÃÂÃÂ²
Weight	34 lb/ft	50.6 kg/m

Elastic Section Properties

Property	Strong Axis (X-X)	Weak Axis (Y-Y)	Unit
Moment of Inertia (I)	137	35.2	in⁴
Elastic Section Modulus (S)	15.6	7.85	in³
Plastic Section Modulus (Z)	27.9	12.3	in³
Radius of Gyration (r)	3.7	1.87	in

Torsional Properties

Property	Value	Unit
Torsional Constant (J)	0.932	in⁴
Warping Constant (Cw)	4.08	in⁶

Section Profile Summary

WT/ST sections are cut from W-shapes — the stem tip was at the mid-depth of the original beam and has the highest residual stresses. For beam applications, orient the stem in tension (pointing down for simply-supported beams). Per AISC 360 Section F9, the flexural capacity depends on whether the stem or flange is in compression.

At 11.9" 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	1,395 kip-in
Deflection	Δ = 5wLÃÂ¢ÃÂÃÂ´/(384EIx)	Use Ix = 137 in⁴
Torsion	St. Venant = GJ/L	J = 0.932 in⁴
Column buckling	KL/r ÃÂ¢ÃÂÃÂ Fcr	r_x = 3.7 in

Design Notes

Stem in tension for beams: Orient the tee so the flange is in compression (stem down for gravity loads). Per AISC 360 Section F9, the flexural capacity is significantly higher with the stem in tension.
Flexural-torsional buckling for columns: Single-axis symmetry means the governing buckling mode may be flexural-torsional rather than pure flexural per AISC 360 Eq. E4-4.
Connection eccentricity: The centroid is closer to the flange — tension connections must account for the induced bending when the work line differs from the centroidal axis.

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: Tension Capacity — wt12x34

Scenario: wt12x34 used as a bottom chord member in a roof truss. The member carries axial tension only under the governing load combination.

Given:

wt12x34: gross area Ag = 10 in²
Steel: Fy = 50 ksi, Fu = 65 ksi
Connection: bolted through the flange with 4 bolts per line (standard holes)

Step 1 — Gross yield (AISC 360 Eq. D2-1):

φTn_yield = 0.9 × Ag × Fy = 0.9 × 10 × 50 = 450 kips

Step 2 — Net section fracture:

For bolted connections, deduct bolt holes from Ag: An = Ag − n × dh × tf

The effective net area Ae = U × An depends on the shear lag factor U per AISC 360 Table D3.1.

Check φTn_fracture = 0.75 × Ae × Fu per AISC 360 Eq. D2-2.

Step 3 — Stem-in-tension note:

For WT/ST sections loaded in axial tension, the eccentricity between the centroid and the connection plane introduces a bending moment that should be considered in the connection design. The stem is more flexible than the flange — verify the weld or bolt group can accommodate the induced prying action.

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.