W8X21 Steel Beam — Section Properties
Dimensions
| Property | Value | Unit |
|---|---|---|
| Depth (d) | 8.28 | in (210.3 mm) |
| Flange Width (bf) | 5.27 | in (133.9 mm) |
| Flange Thickness (tf) | 0.40 | in |
| Web Thickness (tw) | 0.25 | in |
| Area (A) | 6.16 | in² (39.7 cm²) |
| Weight | 21 | lb/ft (31 kg/m) |
Elastic Section Properties
| Property | Strong Axis (X-X) | Weak Axis (Y-Y) | Unit |
|---|---|---|---|
| Moment of Inertia (I) | 75.30 | 9.77 | in⁴ |
| Elastic Section Modulus (S) | 18.20 | 3.71 | in³ |
| Plastic Section Modulus (Z) | 20.40 | 5.69 | in³ |
| Radius of Gyration (r) | 3.49 | 1.26 | in |
Torsional Properties
| Property | Value | Unit |
|---|---|---|
| Torsional Constant (J) | 0.28 | in⁴ |
| Warping Constant (Cw) | 152 | in⁶ |
| Distance Between Flange Centroids (ho) | 7.88 | in |
| Effective Radius (rts) | 1.46 | in |
Design Resources
- Beam Capacity Calculator — Check W8X21 for your span and loads
- Column Capacity Calculator — Check W8X21 as a column
- Section Properties Database — Compare with other sections
- Steel Beam Sizes Reference — Full W-shape dimension table
- Steel Grades Reference — A992/A572 material properties
Frequently Asked Questions
What is the weight of a W8X21 beam? 21 lb/ft (31 kg/m). A 40-ft length weighs approximately 840 lbs.
What is the section modulus of W8X21? Sx = 18.2 in³ (strong axis) and Sy = 3.7 in³ (weak axis). The plastic section modulus Zx = 20.4 in³ and Zy = 5.7 in³.
What steel grade is standard for W8X21? Typically ASTM A992 (Fy = 50 ksi, Fu = 65 ksi) for W-shapes. Also available in A572 Grade 50 or A36. Verify with mill certificate.
What is the moment of inertia of W8X21? Ix = 75.3 in⁴ about the strong axis and Iy = 9.8 in⁴ about the weak axis. The radius of gyration is rx = 3.49 in and ry = 1.26 in.
Related Pages
- Steel Beam Sizes Reference
- Beam Capacity Calculator
- Column Capacity Calculator
- Section Properties Database
Educational reference only. Verify all section properties against the current AISC Manual and mill certificates before design. Results are PRELIMINARY — NOT FOR CONSTRUCTION.