How to Calculate Beam Deflection
What is Beam Deflection?
Beam deflection calculates downward displacement under loading. Engineers use this to ensure beams don't sag excessively and meet serviceability requirements.
Formula
The calculator applies beam deflection formulas: δ = PL³/(3EI) for cantilever
Step-by-Step Guide
- 1Input beam type (cantilever, simply supported, etc.), load type, material properties, and geometry
- 2The calculator applies beam deflection formulas: δ = PL³/(3EI) for cantilever
- 3Results show maximum deflection and compliance with limits
Worked Examples
Input
Cantilever, P=10 kN, L=3 m, EI=200 kN·m²
Result
δ ≈ 45 mm
At L/4 deflection check
Common Mistakes to Avoid
- ✕Using beam formula for wrong support conditions
- ✕Neglecting distributed loads when present
Frequently Asked Questions
Why limit beam deflection?
Excessive deflection causes floor sag, cracks, misalignment. Building codes limit deflection to L/240-L/360.
How does moment of inertia affect deflection?
Doubling I reduces deflection by half; this is why tall I-beams resist deflection better than wide ones.
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