Plate Girder Unit Weight Calculator

Here’s a comprehensive table summarizing all you need to know about plate girder unit weights:

Plate Girder Unit Weight

Aspect	Details
Basic Formula	Weight per unit length = Cross-sectional area × Density of steel
Steel Density	7,850 kg/m³ (490 lb/ft³)5
Components	Web plate, Top flange plate, Bottom flange plate

Typical Dimensions and Weights

Component	Typical Dimensions	Weight Contribution
Web	0.375″ to 0.75″ thick, 24″ to 96″ deep	Major contributor
Flanges	0.75″ to 3″ thick, 12″ to 36″ wide	Significant contributor

Calculation Method

1. Calculate area of each component (web and flanges)
2. Sum the areas
3. Multiply total area by steel density
4. Result is weight per unit length

Factors Affecting Weight

• Web depth and thickness
• Flange width and thickness
• Use of stiffeners or cover plates
• Span length requirements

Comparison with Rolled Beams

Aspect	Plate Girders	Rolled Beams
Customization	Highly customizable	Limited to standard sizes
Weight efficiency	Can be more efficient for long spans	More efficient for shorter spans
Fabrication cost	Higher due to welding	Lower, pre-fabricated

Weight Optimization Techniques

1. Use of high-strength steel to reduce plate thickness
2. Optimizing web and flange dimensions
3. Utilizing tension flange transitions4
4. Considering hybrid designs (different steel grades for web and flanges)

Design Considerations

• AASHTO LRFD Bridge Design Specifications
• Local building codes and standards
• Load requirements (dead load, live load, environmental factors)
• Span length and bridge configuration

Tools for Weight Estimation

• eSPAN140: Free web-based tool for preliminary design of short span steel bridges4
• Steel producers’ weight tables and calculators
• Engineering software for detailed analysis

By using this table and understanding these factors, engineers and designers can effectively estimate and optimize the unit weight of plate girders for various applications, particularly in bridge construction. It’s important to note that while weight reduction is often desirable, it should be balanced with structural requirements, fabrication costs, and overall project economics.