1. The Longest Bridges in the World...

2. The Longest Bridges in the World…

3. The Longest Bridges in the World
Have something in common

4. Suspension Bridges

5. Suspension Bridges
Efficient Structure b/c:

6. Suspension Bridges Efficient Structure b/c: Most members in Tension
Main Cable in Tension
Efficient Structure b/c:
Most members in Tension
Suspenders in Tension

7. Suspension Bridges Efficient Structure b/c: Most members in Tension
Few members in Compression

8. Suspension Bridges Efficient Structure b/c: Most members in Tension
Few members in Compression
Few members in Bending
There are no bending
members in this view

9. Suspension Bridges Bending Member: Girder Spans Between
Suspender Ropes

10. Fill Beams
Girder

11. Fill Beams
Girder

12. Suspension Bridges Bending Member: Girder Spans Between
Suspender Ropes

13. Suspension Bridges Bending Member: Girder Spans Between
Suspender Ropes

14. Suspension Bridges
Other Characteristics

15. Suspension Bridges Other Characteristics: Main Cable in Tension
Suspenders in Tension

16. Suspension Bridges Other Characteristics:
Main Cable in Tension
Other Characteristics:
Demands HUGE Anchorage (Dead Weight)
Suspenders in Tension

17. Suspension Bridges Other Characteristics: W W
Main Cable in Tension
Other Characteristics:
Demands HUGE Anchorage (Dead Weight) W W
Suspenders in Tension

18. Suspension Bridges Other Characteristics: W W
Main Cable in Tension
Other Characteristics:
Demands HUGE Anchorage (Dead Weight)
(Sliding Resistance Must Exceed Cable Force) W W
Suspenders in Tension f N f N

19. Other Characteristics
The Suspended Structure is Unstable

20. Other Characteristics
The Suspended Structure is Unstable
Stiffening trusses needed for stability and lateral stiffness

21. Other Characteristics
Otherwise….
Stiffening trusses needed for stability and lateral stiffness

22. Example 2: The Brooklyn Bridge, Determine Main Cable Force Using Statics

23. Example 2: The Brooklyn Bridge, Determine Main Cable Force Using Statics
Given:
w = 9 kip/ft
h = 160’
2L = 1600’