Here's a clear comparison of steel girder bridge types and their key differences:

Types of Steel Girder Bridges

Key Differences Explained

1. Load Capacity:

   • Rolled I-beams: Simplest, for light loads

   • Plate girders: Customizable for heavy rail/road loads

   • Box girders: Best for combined bending+torsion (e.g., curved bridges)

2. Span Capability:

   • Short (<30m): Rolled beams

   • Medium (30-100m): Plate/box girders

   • Long (>100m): Box girders dominate

3. Fabrication Complexity:

   • Rolled beams: Ready-to-use

   • Plate girders: Field welding/bolting required

   • Box girders: Precision welding of closed sections

4. Economic Factors:

   • Rolled beams: Cheapest upfront

   • Box girders: Higher initial cost but lower life-cycle maintenance

5. Aerodynamics:

   • Open I-girders: Prone to wind vibrations

   • Closed box sections: Better for high-wind areas

Specialized Variants

• Variable Depth Girders: Deeper at supports (optimizes material usage)

• Launching Nose Girders: Tapered front for incremental construction

• Orthotropic Decks: Integrated steel decking (common in box girders)

Selection Guide

• Highway Overpass: Plate girder (cost-effective for 40-60m spans)

• Mountainous Terrain: Box girder (handles curves and torsion)

• Urban Aesthetics: Tub girder (sleek appearance)

• Railway Bridge: Heavy plate girder (fatigue-resistant details)