L8X6X7/8 Steel Angle — Section Properties
Dimensions
| Property | Value | Unit |
|---|---|---|
| Leg Length (leg) | 8 | 20.32 cm |
| Leg Thickness (t) | 0.875 | 2.22 cm |
| Area (A) | 11.5 in² | 74.2 cmÃÂò |
| Weight | 39.1 lb/ft | 58.2 kg/m |
Elastic Section Properties
| Property | Strong Axis (X-X) | Weak Axis (Y-Y) | Unit |
|---|---|---|---|
| Moment of Inertia (I) | 72.4 | 34.9 | in⁴ |
| Elastic Section Modulus (S) | 13.4 | 7.94 | in³ |
| Plastic Section Modulus (Z) | 24.3 | 14.4 | in³ |
| Radius of Gyration (r) | 2.5 | 1.74 | in |
Torsional Properties
| Property | Value | Unit |
|---|---|---|
| Torsional Constant (J) | 2.96 | in⁴ |
| Warping Constant (Cw) | 11.3 | in⁶ |
Section Profile Summary
Angles are asymmetric sections — the shear center is at the intersection of the two legs, not at the centroid. Any load applied through the centroid still produces torsion. For single-angle beams, lateral-torsional buckling must be checked per AISC 360 Eq. F10-4.
Key Design Checks (AISC 360)
| Check | Formula | This Section |
|---|---|---|
| Plastic moment | Mp = Zx × Fy | 1,215 kip-in |
| Deflection | Δ = 5wLâÃÂô/(384EIx) | Use Ix = 72.4 in⁴ |
| Torsion | St. Venant = GJ/L | J = 2.96 in⁴ |
| Column buckling | KL/r âÃÂàFcr | r_x = 2.5 in |
Design Notes
- Single-angle flexure: Use AISC 360 Section F10. Moments are resolved about the principal axes (w-w and z-z), not the geometric axes. The geometric properties above are tabulated for convenience — transform to principal axes for accurate flexure design.
- Leg slenderness: The outstanding leg b/t ratio controls compactness per AISC 360 Table B4.1a, Case 6 (single angle).
- Shear lag in bolted connections: When only one leg is connected, the effective net area per AISC 360 Section D3 accounts for the eccentricity. For welded connections, U depends on the weld length-to-width ratio.
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 Member Check — l8x6x7-8
Scenario: A single angle used as a diagonal tension brace in a braced frame bay. The brace is connected to a gusset plate by welding one leg. Because the connection is eccentric (load applied to one leg only), shear lag reduces the effective net area.
Given:
- l8x6x7-8: gross area Ag = 11.5 in²
- Steel: Fy = 50 ksi, Fu = 65 ksi
- Connection: welded to one leg only
Step 1 — Gross section yield (AISC 360 Eq. D2-1):
φTn_yield = φ × Ag × Fy = 0.9 × 11.5 × 50 = 518 kips
Step 2 — Net section fracture with shear lag (AISC 360 Eq. D2-2):
For a single angle welded to one leg, the shear lag factor U depends on the connection length and eccentricity. Per AISC 360 Table D3.1, for a single angle with 4+ fasteners per line or equivalent weld length, U = 0.80.
Ae = U × An where An = Ag (no bolt holes for welded connection)
φTn_fracture = φ × Ae × Fu = 0.75 × (0.80 × 11.5) × 65 âÃÂà375 kips
Step 3 — Design check:
The smaller of the two limit states governs: φTn = min(yield, fracture) kips. Ensure the factored axial demand (from wind or seismic load combinations) does not exceed this value. Also verify the gusset plate weld length develops the required force.
Related Resources
- Steel Beam Capacity Calculator
- Column Capacity Calculator
- Beam Deflection Calculator
- Section Properties Calculator
- Steel Grades Reference
- Section Comparison Tool
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.