1. What is the Required Moment of Inertia?

The required moment of inertia (I_req) is a calculation that determines the stiffness needed for a beam to resist deflection under a given load. This helps engineers select the appropriate size of engineered wood beams for construction projects.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• \( w \) — Uniform load (pounds per linear foot)
• \( L \) — Span length (feet)
• \( E \) — Modulus of elasticity (pounds per square inch)
• \( \delta_{max} \) — Maximum allowable deflection (inches)

Explanation: The equation calculates the minimum moment of inertia required to keep beam deflection within acceptable limits for a given load and span.

3. Importance of Beam Sizing

Details: Proper beam sizing is critical for structural integrity, safety, and compliance with building codes. Undersized beams can lead to excessive deflection or failure, while oversized beams are unnecessarily expensive.

4. Using the Calculator

Tips: Enter the uniform load in pounds per linear foot, span length in feet, modulus of elasticity in psi, and maximum allowable deflection in inches. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical modulus of elasticity for engineered wood?
A: Values typically range from 1,200,000 psi for LVL to 1,800,000 psi for some types of glulam beams.

Q2: What are common deflection limits?
A: L/360 is common for floors (e.g., 0.53" for 16' span), L/240 for roofs, and L/180 for garage floors.

Q3: Does this account for shear deflection?
A: No, this calculation only considers bending deflection. Shear deflection may need separate consideration.

Q4: How do I convert total load to uniform load?
A: Divide total load by span length (e.g., 2000 lb over 10 ft = 200 plf).

Q5: Should I include safety factors?
A: This calculation gives theoretical values. Always consult building codes and apply appropriate safety factors.