Overview of Deck Truss Structural Components

Support System

• Piers: Bridge supported on four piers, numbered 5 to 8 from south.
  • Pier 7: Located on the north side of the river with a fixed bearing.
    • No movement mechanism relative to the pier.
  • Piers 5, 6, and 8: Equipped with roller bearings.
    • Allow thermal expansion and contraction of the deck truss.

Truss Structure

• Main Trusses: Two main trusses, total length 1,064 feet.
  • Serve as the primary support for the bridge deck.
  • Design: Non-redundant, meaning failure of a single member results in bridge collapse.
  • Span Measurements:
    • Center span: 456 feet across the Mississippi River.
    • North and south spans: Each 304 feet.
• Composition: Four types of members.
  • Upper cord members
  • Lower cord members
  • Diagonal members
  • Vertical members

Connection and Nodes

• Nodes: Truss members connected at nodes using gusset plates.
  • Numbered from 0 (south end) to 14 (center), with north-to-south symmetry.
  • Prime sign indicates nodes north of the center.
  • Upper nodes prefix: U
  • Lower nodes prefix: L
• Gusset Plates
  • Thickness: 0.5 to 1 inch
  • Connection: Riveted, some bolts used.
  • Example: Node U10 plates are 0.5 inch thick, ~9 feet long, >6 feet high.

Load and Bracing

• Load Types on Truss Members
  • Compression: Shown in blue
  • Tension: Shown in red
  • Example: Node U10 has two members under compression, three under tension.
• Stabilization
  • Floor trusses between main trusses support the bridge deck.
  • Lateral and sway braces at each node stabilize structure.
• Deck Support
  • 14 deck stringers above the floor trusses support the reinforced concrete deck.

Deck Design

• Originally designed to be 6 inches thick.
• Two slabs: Northbound and southbound lanes.
• Includes median barriers and steel guard rails.