Cantilever vs Simply Supported Beams: Design Considerations
Cantilever vs Simply Supported Beams
Understanding the differences between beam support conditions is fundamental to structural design. Each configuration has unique characteristics affecting load capacity and deflection.
Simply Supported Beams
A simply supported beam rests on two supports at its ends, free to rotate but not translate.
Characteristics:
- Zero moment at supports
- Maximum moment at center (for center load)
- Deflection formula: δ = PL³/48EI (center point load)
Advantages:
- Simple construction
- Easy analysis
- Allows thermal expansion
- Lower support reactions
Applications:
- Bridge spans
- Floor joists
- Simple roof structures
Cantilever Beams
A cantilever beam is fixed at one end and free at the other, fully restraining rotation and translation at the support.
Characteristics:
- Maximum moment at fixed support
- Higher deflection than simply supported
- Deflection formula: δ = PL³/3EI (end load)
Advantages:
- No intermediate supports needed
- Creates overhangs
- Clear span below
Applications:
- Balconies
- Canopies
- Sign structures
- Diving boards
Comparison Table
Design Recommendations
- Use simply supported for longer spans
- Use cantilevers for overhangs and projections
- Consider fixed-end beams for reduced deflection
- Always check deflection limits per code requirements