Pratt Truss vs Howe Truss: Key Differences
Both Pratt and Howe trusses are fundamental bridge designs using triangular elements. The main difference lies in how tension and compression forces are distributed through their diagonal members.
Pratt Truss Design
- Diagonal members slope downward from top chord to bottom chord
- Vertical members handle tension forces
- Efficient for longer spans
- Commonly used in railroad bridges
Howe Truss Design
- Diagonal members slope upward from top chord to bottom chord
- Vertical members handle compression forces
- Better for shorter spans
- Popular in early 19th century construction
Comparison Table
| Feature | Pratt Truss | Howe Truss | Key Difference |
|---|---|---|---|
| Diagonal Slope | Downward | Upward | Force distribution direction |
| Span Length | Longer spans | Shorter spans | Structural efficiency |
| Construction Cost | Moderate | Lower | Material usage |
| Modern Usage | Railroad bridges | Historic structures | Application focus |
When to Choose Each Truss
- Choose Pratt for longer spans requiring maximum efficiency
- Select Howe for shorter spans where cost is primary concern
- Consider Pratt for modern steel bridges
- Use Howe for historical restoration projects