W21X55 Steel Beam — Section Properties
Dimensions
| Property | Value | Unit |
|---|---|---|
| Depth (d) | 20.80 | in (528.3 mm) |
| Flange Width (bf) | 8.22 | in (208.8 mm) |
| Flange Thickness (tf) | 0.52 | in |
| Web Thickness (tw) | 0.38 | in |
| Area (A) | 16.20 | in² (104.5 cm²) |
| Weight | 55 | lb/ft (82 kg/m) |
Elastic Section Properties
| Property | Strong Axis (X-X) | Weak Axis (Y-Y) | Unit |
|---|---|---|---|
| Moment of Inertia (I) | 1,140 | 48.40 | in⁴ |
| Elastic Section Modulus (S) | 110 | 11.80 | in³ |
| Plastic Section Modulus (Z) | 126 | 18.40 | in³ |
| Radius of Gyration (r) | 8.40 | 1.73 | in |
Torsional Properties
| Property | Value | Unit |
|---|---|---|
| Torsional Constant (J) | 1.24 | in⁴ |
| Warping Constant (Cw) | 4,980 | in⁶ |
| Distance Between Flange Centroids (ho) | 20.30 | in |
| Effective Radius (rts) | 2.11 | in |
Design Resources
- Beam Capacity Calculator — Check W21X55 for your span and loads
- Column Capacity Calculator — Check W21X55 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 W21X55 beam? 55 lb/ft (82 kg/m). A 40-ft length weighs approximately 2,200 lbs.
What is the section modulus of W21X55? Sx = 110 in³ (strong axis) and Sy = 11.8 in³ (weak axis). The plastic section modulus Zx = 126 in³ and Zy = 18.4 in³.
What steel grade is standard for W21X55? 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 W21X55? Ix = 1140 in⁴ about the strong axis and Iy = 48.4 in⁴ about the weak axis. The radius of gyration is rx = 8.40 in and ry = 1.73 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.