1. What is the Steel Beam Deflection Formula?

The steel beam deflection formula calculates the required moment of inertia (I) for a simply supported beam under uniform load to meet specified deflection criteria. It's essential for structural design to ensure beams meet serviceability requirements.

2. How Does the Calculator Work?

The calculator uses the deflection formula:

Where:

• \( I_{req} \) — Required moment of inertia (in⁴)
• \( w \) — Uniform load (pounds per linear foot)
• \( L \) — Span length (feet)
• \( E \) — Modulus of elasticity (psi, typically 29,000,000 for steel)
• \( \delta_{max} \) — Maximum allowable deflection (inches)

Explanation: The formula calculates the minimum moment of inertia needed to limit deflection to the specified maximum under the given loading conditions.

3. Importance of Moment of Inertia

Details: The moment of inertia (I) is a critical property that determines a beam's resistance to bending and deflection. Proper selection ensures structural integrity and serviceability.

4. Using the Calculator

Tips: Enter uniform load in plf, span length in feet, modulus of elasticity in psi (default is 29,000,000 for steel), and maximum allowable deflection in inches. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical deflection limit?
A: Common limits are L/360 for floors (max δ = L*12/360) or L/240 for roofs, where L is span in feet.

Q2: How do I convert kN/m to plf?
A: Multiply kN/m by 68.5218 to get plf (1 kN/m ≈ 68.5218 plf).

Q3: What's the modulus of elasticity for steel?
A: Typically 29,000,000 psi (29,000 ksi) for structural steel.

Q4: Can this be used for other materials?
A: Yes, but use the appropriate E value (e.g., 1,800,000 psi for wood).

Q5: How do I select a beam after calculating I_req?
A: Consult steel section tables (e.g., AISC Manual) and choose a section with I ≥ I_req.