INDUSTRY COMPONENT

Bottom Flange

Bottom flange is the lower horizontal structural element of a bridge girder that resists compressive forces and provides stability.

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Component Specifications

Definition
The bottom flange is a critical structural component in bridge girders, typically an I-beam or box girder configuration, designed to withstand compressive stresses from bending moments. It works in conjunction with the top flange and web to distribute loads efficiently across the span, ensuring structural integrity and load-bearing capacity. In most bridge designs, the bottom flange experiences compression when the girder is subjected to positive bending moments (sagging).
Working Principle
The bottom flange functions as part of the girder's flexural system, resisting compressive forces through its cross-sectional area and material strength. When the girder bends under load, the bottom flange compresses while the top flange experiences tension, creating a force couple that maintains structural equilibrium. The flange's width and thickness are engineered to prevent buckling and ensure stable load transfer to supports.
Materials
Typically ASTM A572 Grade 50 or A709 Grade 50 steel for highway bridges, or higher grades for heavy-load applications. European equivalents include S355J2 or S460ML. Material must meet specific yield strength (min 345 MPa), tensile strength, and toughness requirements for bridge applications.
Technical Parameters
  • Width 300-1200 mm
  • Thickness 20-100 mm
  • Surface Finish SA 2.5 blasted, primed
  • Yield Strength ≥345 MPa
  • Corrosion Protection Hot-dip galvanized or painted per ASTM A123
Standards
ISO 10721, DIN 18800, AASHTO LRFD, EN 1993-1-1

Industry Taxonomies & Aliases

Commonly used trade names and technical identifiers for Bottom Flange.

bridge girder bottom flange structural steel flange compression flange I-beam flange bridge construction components steel girder design Bottom Flange Bottom Flange in Machinery and Equipment Manufacturing

Parent Products

This component is used in the following industrial products

Bridge Girder

The primary horizontal structural beam of an overhead crane that supports the trolley and hoist.

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Holder/Flange Assembly

A mechanical assembly that secures and seals a rupture disc within a pressure system.

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Engineering Analysis

Risks & Mitigation
  • Buckling under compression
  • Fatigue cracking at connections
  • Corrosion in harsh environments
  • Weld defects leading to structural failure
FMEA Triads
Trigger: Inadequate thickness for design loads
Failure: Local buckling or yielding
Mitigation: Follow AASHTO LRFD design specifications with appropriate safety factors, conduct finite element analysis
Trigger: Poor weld quality at flange-web connection
Failure: Crack propagation leading to structural collapse
Mitigation: Implement AWS D1.5 welding procedures, perform non-destructive testing, certify welders
Trigger: Insufficient corrosion protection
Failure: Section loss reducing load capacity
Mitigation: Apply appropriate coating systems, implement regular inspection schedules, use weathering steel where applicable

Industrial Ecosystem

Compatible With

Interchangeable Parts

Compliance & Inspection

Tolerance
±2 mm for thickness, ±3 mm for width, ±1.5 mm for flatness over 3m length
Test Method
Ultrasonic testing per ASTM A435, tensile testing per ASTM A370, Charpy V-notch impact testing per ASTM A673

Buyer Feedback

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"The technical documentation for this Bottom Flange is very thorough, especially regarding technical reliability."

"Reliable performance in harsh Machinery and Equipment Manufacturing environments. No issues with the Bottom Flange so far."

"Testing the Bottom Flange now; the technical reliability results are within 1% of the laboratory datasheet."

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Frequently Asked Questions

What is the primary function of a bottom flange in bridge construction?

The bottom flange primarily resists compressive forces during positive bending moments, working with the web and top flange to maintain structural stability and distribute loads across the bridge span.

How are bottom flanges connected to other girder components?

Bottom flanges are typically welded to the web using full-penetration groove welds or connected with high-strength bolts in splice connections, following AWS D1.5 or EN ISO 5817 standards for bridge welding.

What inspection is required for bottom flanges during installation?

Visual inspection for defects, ultrasonic testing for weld quality, dimensional verification per design drawings, and coating thickness measurement for corrosion protection systems.

Can I contact factories directly?

Yes, each factory profile provides direct contact information.

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