Structural & Civil Engineering

What is the mid-span deflection of a W12x26 beam spanning 7.0 meters under 25.0 kN/m?

⚡ Instant Calculated Answer

A W12x26 steel beam across a 7.0 meter span under a 25.0 kN/m uniform distributed load deflects by 46.03 mm at mid-span, which EXCEEDS the standard building code L/360 serviceability limit (19.44 mm).

46.03 mm Primary Metric
Limit: 19.44 mm Secondary Metric

📐 Mathematical Formula & Step-by-Step Substitution

\[ \delta_{max} = \frac{5 \cdot w \cdot L^4}{384 \cdot E \cdot I_x} = \frac{5 \cdot 25000 \cdot (7.0)^4}{384 \cdot (200 \times 10^9) \cdot (8.49e-05)} = 46.03 \text{ mm} \]
delta = (5 * 25000.0 * 7.0^4) / (384 * 200e9 * 8.49e-05) = 46.03 mm
  1. Identify beam properties: Section W12x26, Moment of Inertia I_x = 8,490 cm⁴ (8.4900e-05 m⁴), Young's Modulus E = 200 GPa.
  2. Convert units: Span L = 7.0 m, Load w = 25.0 kN/m = 25,000 N/m.
  3. Calculate numerator: 5 × 25,000 × (7.0)⁴ = 5 × 25,000 × 2401.00 = 300,125,000.0.
  4. Calculate denominator: 384 × 200×10⁹ × 8.4900e-05 = 6,520,320,000.0.
  5. Evaluate deflection: 300,125,000.0 / 6,520,320,000.0 = 0.04603 m = 46.03 mm (compared to L/360 = 19.44 mm).

📊 Nearby Parameter Reference Table

Span Length Uniform Load Mid-Span Deflection L/360 Code Limit
6.0 m 25.0 kN/m 24.85 mm 16.67 mm (FAIL)
6.5 m 25.0 kN/m 34.22 mm 18.06 mm (FAIL)
7.0 m 25.0 kN/m 46.03 mm 19.44 mm (FAIL)
7.5 m 25.0 kN/m 60.66 mm 20.83 mm (FAIL)
8.0 m 25.0 kN/m 78.52 mm 22.22 mm (FAIL)
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