Bridge Introduction

2. Ponte d’Angelo, Rome, built in 136 AD

4. John Roebling, Brooklyn Bridge, 1883 (14 years under construction)
1,600 ft span (488 m), 4 cables (diameter) width 85‘ (26 m), cost $9 million

5. Verrazano Narrows Bridge,
New York – New Jersey

6. Sunshine Skyway Bridge
Tampa, Florida

8. Importance of Bridges
• Bridges are structures with span larger than
20 ft (6m)
• There are 584,000 bridges in USA (4 million
paved roadway
• Interstate highway network consists of
45,750miles (73,200 km) of highways and
54,800 bridges
• Traffic growth: number of vehicles and weight
of trucks

10. ASCE Report Card
average = D+
presented to US Congress
• Roads
– 1/3 major roads in poor mediocre condition
– Cost to drivers: $5.8 billion/year, 14,000 fatalities/year
– 27% freeways congested
• Bridges
– 29% structurally deficient or functionally obsolete
– Estimated cost of repair: $10.6 billion/year for next 20 years
• Drinking Water
– Cost to replace drinking water facilities to comply with federal water
regulations = $11 billion/year
• Dams
– 2100 unsafe dams
– 61 reported failures in last 2 years

11. General Problems
• Most bridges were built in 1950’s and 1960’s
• Bridges deteriorate due to aging, increased live
loads, cracking, corrosion, environmental effects
(freeze and thaw cycles), fatigue
• Many bridges (30%) need repair, rehabilitation
or replacement
• Available funds are limited. How to use the
limited resources in the most efficient way?

12. Causes of failures:
Extreme events and other threats
• Natural disasters: hurricanes, floods,
earthquakes, major storms
• Improper maintenance, negligence
(corrosion, cracking, other forms of
deterioration)
• Overloads (e.g. overloaded trucks)
• Collisions and fire
• Human errors (during design and
construction)
• Vandalism and terrorist attacks

13. Schoharie Creek Bridge

16. Depth of Scour

17. Damaged Plinth

23. 23

24. 24

25. 25

26. 26

27. 27

29. Needs
• Rational bridge design codes
• Efficient procedures for evaluation of
existing bridges (actual loads, actual
load carrying capacity)
• Efficient methods for repair and
rehabilitation
• Methods for prediction of future changes

30. Golden Gate Bridge
San Francisco

31. Current Trends
• Reliability-based design codes, load and
resistance factor design (LRFD)
• Weigh-in-motion (WIM) truck surveys
• Advanced finite element methods (FEM)
• Non-destructive evaluation techniques
(NDT)
• Bridge management system (BMS)
• Repair, rehabilitation and replacement

32. Future Developments
• Performance-based design
• Life-cycle optimization
• High-performance materials
• Computer-aided analysis and design
• Remote sensing and monitoring of
structural performance
• Security considerations
• Minimization of interference with traffic

33. Administration of Bridges
• Federal
• State
• County
• City
• Private owners

34. Federal
Levels
• US Department of Transportation (DOT)
• Federal Highway Administration (FHWA)
• Regional Offices
Role
• Coordinate national programs
• Provide funds for bridges owned by
States
• Enforce code requirements

35. State
• State Department of Transportation
• State DOT’s own about 50% of bridges
in USA
• Management of bridges (planning,
design, construction, operation,
inspection, maintenance, repairs,
demolition)
• Each State DOT is represented in
AASHTO (American Association of State
Highway and Transportation Officials)

36. Counties and Cities
• They own the remaining 50% of bridges
• Insufficient budgets for inspections and
repairs
• Often poor maintenance
• Bridges that belong to counties and cities
are often in poor condition

37. AASHTO
American Association of State Highway
and Transportation Officials
• Each State has a vote (including D.C. and P.R.)
• AASHTO issues bridge design codes
• Manual for evaluation of bridges
• Design guides (e.g. seismic design, segmental
bridges, curved girder bridges)
• Selects bridge related research problems for funding

38. FHWA National Bridge Inventory
• Total number of bridges in NBI is 584,000
• Federal Aid Highway Bridges – owned by State
DOT’s (about 50%)
• Off System Highway Bridges – owned by Counties,
Cities and private owners
• FHWA maintains a National Bridge Inventory which
includes bridge registration number, location,
structural type, material, number of spans, span
length(s), width, and rating factors