Flecha viga madeira
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The 'Wooden beam deflection' calculator determines the maximum deflection of a wooden beam supported at both ends under uniform distributed load. The formula δ = 5qL⁴/(384EI) calculates this deflection using linear load (q), beam length (L), modulus of elasticity (E), and cross-sectional moment of inertia (I). It's critical for construction projects involving wooden structures, ensuring beams meet safety and stability criteria.
To use the calculator, input precise data such as wood type (to determine E), beam dimensions (to calculate I), and supported load. The result helps verify if the calculated deflection aligns with acceptable limits set by technical standards (e.g., NBR 7190). The formula assumes the beam is homogeneous, elastic, and under uniform load, making it invalid for non-linear bending or complex loading scenarios.
This tool is particularly useful in civil works, renovations, and wooden structure manufacturing. For instance, when designing a wooden roof slab, the calculator predicts whether the beam will maintain required rigidity without excessive deformation. Remember that the wood's modulus of elasticity varies by type (e.g., Pine vs. Eucalyptus) and moisture content, directly affecting result accuracy.
The calculator does not replace analysis by a structural engineer, especially for critical cases. Validate calculations with advanced simulations or consult region-specific standards. Additionally, the formula overlooks factors like wood aging, thermal cycles, or natural imperfections that may impact real-world durability.
Frequently asked questions
What measurement units should I use in the calculator fields?
Use compatible units: load in kN/m, length in meters, E in MPa, and moment of inertia in cm⁴. Convert units to match before entering values.
What is the modulus of elasticity (E), and how do I find it for different wood types?
E measures wood stiffness. Typical values range from 6,000 MPa (Pine) to 10,000 MPa (Eucalyptus). Check mechanical property tables or technical standards like NBR 7190.
Why does the moment of inertia depend on the beam's cross-section?
The moment of inertia (I) is a geometric property that varies with cross-sectional width, height, and shape (e.g., rectangular, I-beam). The formula assumes uniform material distribution around the neutral axis.
When should I avoid using this formula?
Avoid it for beams with concentrated loads, more than two supports, or dynamic loads (e.g., vibrations). Use advanced structural analysis methods in those cases.
How do I compare the calculated deflection with code limits?
Divide the beam span (L) by the code-specified ratio (e.g., L/300 or L/400 per NBR 7190). If the calculated deflection is larger, redesign with larger dimensions or stiffer wood.