bridge

1. Bridge Type SelectionBridge Type Selection
And Engineering OverviewAnd Engineering Overview

2. "When the history of our time
is written, posterity will know
us not by a cathedral or
temple, but by a bridge."
- Montgomery Schuyler, 1877
writing about the Brooklyn Bridge

3. Bridges & Society

4. Typical Bridge Process
●●Bridge Design
●●
●Bridge Type Study
●ROD
●Preferred Alignment/Location
●●Public Hearings
●●●●●●●●●●Stakeholder/Community Input
Final DesignPreliminary Design
NEPA
EIS & Location
Study

5. Bridge Design Process
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Bridge Concepts
Geotechnical
Investigation
Hydraulic Design
Design
Surveys
Alignment
Concepts
Preliminary
Alignment
Identify Potential
Bridge Types
EIS / Agency
Review &
Approval
ROD
Structural
Design
Plan
Preparation
Preliminary
Bridge Design
Construction

6. Bridge Design Process
??
??
??
Bridge Concepts
Geotechnical
Investigation
Hydraulic Design
Design
Surveys
Alignment
Concepts
Preliminary
Alignment
Identify Potential
Bridge Types
EIS / Agency
Review &
Approval
ROD
Structural
Design
Plan
Preparation
Preliminary
Bridge Design
Construction

7. Identify Potential Bridge
Types for Each Alignment
Screen
• Preliminary Design
• Quantities
• Cost Estimates
• Construction Costs
Screen
Screening
Criteria
• Engineering
Constraints
• Aesthetics
• Contextual
Integration
• Costs
• Environmental
Impacts
• Agency Input
• Stakeholder
Input
Possible
Bridge Types
Feasible
Bridge
Types
Selected
Bridge
Types
Typical Bridge Type Selection Process

8. Screening of Alternatives

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Concrete Slab
PPC Double-Tee
PPC I-/ U-Beam
Conc.Spl.Girder
Segmental Concrete
Steel Girder
Steel Truss
Tied/ True Arch
Cable Stay
Suspension
Possible Spans Optimal Spans
Bridge Types &
Optimal Span Lengths
25’ – 40’
40’ – 60’
40’ – 125’
125’ – 350’
150’ – 500’
150’ – 450’
400’ – 1000’
400’ – 1200’
750’ – 2000’
1500’ – 3000’ +

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Concrete Slab
PPC Double-Tee
PPC I-/ U-Beam
Conc.Spl.Girder
Segmental Concrete
Steel Girder
Steel Truss
Tied/ True Arch
Cable Stay
Suspension
Bridge Types &
Optimal Span Lengths
25’ – 40’
40’ – 60’
40’ – 125’
125’ – 350’
150’ – 500’
150’ – 450’
400’ – 1000’
400’ – 1200’
750’ – 2000’
1500’ – 3000’ +
Possible Spans Optimal Spans Minimum Main Span SDEIS Spans

11. Abernethy Bridge, 1970 – Steel Haunched Girder
Girder Bridges

12. Girder Bridges

13. Girder Bridges
• Steel or Concrete
• I-Girders or Box Girders
• Easy to fabricate
• Easy to erect
• Replaceable slab
• Redundancy
• Unobstructed motorist view
• Longer spans require deeper sections
• Longer spans may require temporary falsework
for erection
• Easy to widen in the future

14. Segmental Concrete

15. Segmental Concrete Bridges
• Cast-in-Place vs. Precast
• Erected in segments without falsework
• Balanced Cantilever vs. Span by Span
• Durability and maintenance
• Deck integral with structure
• Efficient for long spans/bridge lengths
• Difficult to widen in the future

16. Truss Bridges

17. Truss Bridges
Sellwood Br. (1925) - Deck Truss
Broadway Br. (1913) - Through Truss (double-leaf bascule center
span)
Marquam Br. (1966) - Deck Truss

18. Truss Bridges

19. Truss Bridges
• Economical for longer spans vs. Girder Bridges
• Thru Truss vs. Deck Truss
• Prevalent for Oregon crossings 1920s-1930s
• Thru truss allows reduced section under the deck
• Potentially higher maintenance and inspection
costs
• Difficult to widen in the future

20. Arch Bridges

21. Arch Bridges
Ross Island Br. (1926) - Deck Trussed Arch Fremont Br. (1973) - Continuous Through Arch
Sauvie Island Br. (200?) - Tied Arch (behind)

22. Arch Bridges

23. Arch Bridges
• Thru Arch vs. Deck Arch
• True (Thrust) Arch vs. Tied Arch
• Steel vs. Concrete
• Foundation Requirements
• Erection: Tiebacks, Float-in
• Replaceable Deck
• Difficult to widen in the future

24. Cable-Stayed Bridges

25. Cable-Stayed Bridges

26. Cable-Stayed Bridges
• Successor to the suspension bridge for spans up
to 2000-ft
• Greater stiffness
• Steel vs. Concrete
• Roadway deck integral to structure
• Cantilevered construction helps environmental
impacts
• Difficult to widen in the future

27. Suspension Bridges
St. Johns Bridge (1931) – Suspension Bridge

28. Suspension Bridges

29. Suspension Bridges
• Economical for long spans over 2000-ft
• Efficient use of material
• Well known construction method
• Highest cost among cable-supported bridges
• Susceptible to dynamic vibrations
• Higher maintenance and inspection costs
• Difficult to widen in the future

30. Moveable Bridges

31. Moveable Bridges
Morrison Bridge (1958) – Double Leaf Bascule
Burnside Bridge (1926) – Double Leaf BasculeBroadway Bridge (1913) – Double Leaf Bascule
Steel Bridge (1912) – Vertical Lift Bridge

32. Moveable Bridges
Hawthorne Bridge (1910) – Vertical Lift Bridge

33. Moveable Bridges

34. Movable Bridges
• Low rise bridge shortens the overall crossing
length
• Well known bridge type
• Difficult to achieve desired bridge aesthetics
• Marine traffic typically has priority over bridge
traffic
• Higher maintenance and inspection costs
• Difficult to widen in the future
• Poor seismic performance