W8X31 Steel Beam — Section Properties
Dimensions
| Property | Value | Unit |
|---|---|---|
| Depth (d) | 8 | in (203.2 mm) |
| Flange Width (bf) | 8 | in (203.2 mm) |
| Flange Thickness (tf) | 0.43 | in |
| Web Thickness (tw) | 0.28 | in |
| Area (A) | 9.13 | in² (58.9 cm²) |
| Weight | 31 | lb/ft (46 kg/m) |
Elastic Section Properties
| Property | Strong Axis (X-X) | Weak Axis (Y-Y) | Unit |
|---|---|---|---|
| Moment of Inertia (I) | 110 | 37.10 | in⁴ |
| Elastic Section Modulus (S) | 27.50 | 9.27 | in³ |
| Plastic Section Modulus (Z) | 30.40 | 14.10 | in³ |
| Radius of Gyration (r) | 3.47 | 2.02 | in |
Torsional Properties
| Property | Value | Unit |
|---|---|---|
| Torsional Constant (J) | 0.54 | in⁴ |
| Warping Constant (Cw) | 530 | in⁶ |
| Distance Between Flange Centroids (ho) | 7.57 | in |
| Effective Radius (rts) | 2.26 | in |
Design Resources
- Beam Capacity Calculator — Check W8X31 for your span and loads
- Column Capacity Calculator — Check W8X31 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 W8X31 beam? 31 lb/ft (46 kg/m). A 40-ft length weighs approximately 1,240 lbs.
What is the section modulus of W8X31? Sx = 27.5 in³ (strong axis) and Sy = 9.3 in³ (weak axis). The plastic section modulus Zx = 30.4 in³ and Zy = 14.1 in³.
What steel grade is standard for W8X31? 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 W8X31? Ix = 110 in⁴ about the strong axis and Iy = 37.1 in⁴ about the weak axis. The radius of gyration is rx = 3.47 in and ry = 2.02 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.