What is the mid-span deflection of a W8x18 beam spanning 6.0 meters under 20.0 kN/m?
⚡ Instant Calculated Answer
A W8x18 steel beam across a 6.0 meter span under a 20.0 kN/m uniform distributed load deflects by 65.41 mm at mid-span, which EXCEEDS the standard building code L/360 serviceability limit (16.67 mm).
65.41 mm
Primary Metric
Limit: 16.67 mm
Secondary Metric
📐 Mathematical Formula & Step-by-Step Substitution
- Identify beam properties: Section W8x18, Moment of Inertia I_x = 2,580 cm⁴ (2.5800e-05 m⁴), Young's Modulus E = 200 GPa.
- Convert units: Span L = 6.0 m, Load w = 20.0 kN/m = 20,000 N/m.
- Calculate numerator: 5 × 20,000 × (6.0)⁴ = 5 × 20,000 × 1296.00 = 129,600,000.0.
- Calculate denominator: 384 × 200×10⁹ × 2.5800e-05 = 1,981,440,000.0.
- Evaluate deflection: 129,600,000.0 / 1,981,440,000.0 = 0.06541 m = 65.41 mm (compared to L/360 = 16.67 mm).
📊 Nearby Parameter Reference Table
| Span Length | Uniform Load | Mid-Span Deflection | L/360 Code Limit |
|---|---|---|---|
| 5.0 m | 20.0 kN/m | 31.54 mm | 13.89 mm (FAIL) |
| 5.5 m | 20.0 kN/m | 46.18 mm | 15.28 mm (FAIL) |
| 6.0 m | 20.0 kN/m | 65.41 mm | 16.67 mm (FAIL) |
| 6.5 m | 20.0 kN/m | 90.09 mm | 18.06 mm (FAIL) |
| 7.0 m | 20.0 kN/m | 121.17 mm | 19.44 mm (FAIL) |
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