1. What is the Beam Deflection Equation?

The beam deflection equation calculates the maximum deflection (δ) of a simply supported wood beam under uniform load. This is important for ensuring structural integrity and serviceability of wood framing members.

2. How Does the Calculator Work?

The calculator uses the beam deflection equation:

Where:

• \( \delta \) — Maximum deflection (in)
• \( w \) — Uniform load (pounds per linear foot)
• \( L \) — Span length (feet)
• \( E \) — Modulus of elasticity (psi)
• \( I \) — Moment of inertia (in⁴)

Explanation: The equation calculates the midspan deflection of a simply supported beam with uniformly distributed load. The 5/384 factor comes from the integration of the bending moment equation.

3. Importance of Deflection Calculation

Details: Deflection limits are often more critical than strength requirements in wood design. Excessive deflection can cause cracking of finishes, poor drainage, or uncomfortable floor vibrations.

4. Using the Calculator

Tips: Enter all values in consistent units (w in plf, L in ft, E in psi, I in in⁴). Typical E values for wood range from 1,000,000 to 1,800,000 psi depending on species and grade.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical deflection limit?
A: For floors, L/360 is common. For roofs, L/240 or L/180 may be used depending on the application.

Q2: Does this work for concentrated loads?
A: No, this equation is for uniform loads only. Different equations exist for concentrated loads.

Q3: What affects modulus of elasticity (E)?
A: Wood species, grade, moisture content, and duration of load all affect E values.

Q4: How do I find moment of inertia (I) for a wood beam?
A: For rectangular sections, I = (b × h³)/12 where b is width and h is depth. Standard lumber I values are published in tables.

Q5: Does this account for creep deflection?
A: No, this calculates immediate elastic deflection. Wood exhibits time-dependent creep deflection under sustained loads.