1. Suspension Bridges

2. Suspension Bridges
Efficient Structure b/c:

3. 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

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

5. 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

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

7. Fill Beams
Girder

8. Fill Beams
Girder

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

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

11. Suspension Bridges
Other Characteristics

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

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

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

15. 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

16. Other Characteristics
The Suspended Structure is Unstable

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

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

19. Example 1: The Brooklyn Bridge, Determine Main Cable W Using Statics

20. Example 1: The Brooklyn Bridge, Determine Main Cable W Using Statics
Given:
w = 9 kip/ft
h = 160’
2L = 1600’

21. Example 1: The Brooklyn Bridge, Determine Main Cable W Using Statics
Also Given: Main Cable Ultimate Strength Fu = 160 ksi
Cable A = 600 in2
Given:
w = 9 kip/ft
h = 160’
2L = 1600’

22. Example 1: The Brooklyn Bridge, Determine Main Cable W Using Statics
Also Given: Main Cable Ultimate Strength Fu = 160 ksi
Cable A = 600 in2
=> Pn = (160)(600) = kips
Given:
w = 9 kip/ft
h = 160’
2L = 1600’