1. BRIDGES
Beauty and Function

2. Photographed? Jumped off of? Walked across? Driven over?
What Bridges Have YOU…
Photographed?
Jumped off of?
Driven over?
Walked across?
Seen with your own eyes?

3. HISTORY
The first bridges were nature-made: trees that fell across creeks or rivers.
The first man-made bridges were most likely made from trees lashed, stones, or vines.

4. ROMANS
Designed amazing arch bridges and viaducts that could withstand nearly anything when other bridges continued to fail.
The Romans discovered the strength of the arch.
The Alcantara bridge, built in 106 A.D. is still standing today – almost 2,000 years later!

6. FORCES ACTING ON A BRIDGE
Compression – when material squeezes together
Tension - when material pulls apart
Bending – when material gets shorter on one side and longer on the other
Shearing – when material slides in opposite directions
Twisting – when the ends of a material twists in opposite directions

7. BALANCING THE FORCES
A good bridge keeps all the forces in balance; if there is compression there is and equal amount of tension.

8. BRIDGE TYPES BEAM BRIDGE Made of steel, concrete, or wood
Typically shorter than 250’
The longest is the Lake Ponchartrain Causeway, at just under 24 MILES long!

9. TRUSS BRIDGE
A simple but very strong bridge type made of connected triangle shapes, called a “truss”.
The trusses can be above or below the roadbed.
The World’s longest truss bridge is the Itiksuki Bridge in Japan.

10. ARCH BRIDGE Arch bridges have “abutments” at each end.
The weight of the bridge is forced into and supported by these abutments.
The longest arch bridge in the world is the Chaotianmen Bridge in China. It is 5,712’ long!

11. SUSPENSION BRIDGE
The roadbed of a suspension bridge is supported by cables hanging down from one huge cable spanning between the vertical towers.
The road is “suspended” from these cables.
The world’s longest is the Akashi Kaikyo Bridge in Japan at 12,825 feet!

12. CABLE-STAYED BRIDGE
Use less cable than a suspension bridge by having taller towers and cables that connect to the roadbed beneath it.
The world’s longest cable-stayed bridge is the Sutong Bridge in China at 26,923 feet!

13. Famous American Bridges

14. Golden Gate Bridge, S.F.

15. Sunshine Skyway - FL

16. George Washington - NY

17. Brooklyn Bridge - NY

18. Seven Mile Bridge
Connects mainland Florida to the Florida Keys

19. Tacoma Narrows Bridge
Do you know what it is famous for?

20. The Tacoma Narrows Collapse
1940
“Galloping Gertie”

21. The original bridge collapsed due to HARMONIC RESONANCE.
A replacement bridge (green one, on right) was built in 1950.
A second bridge was built in 2007 when traffic increased in the area.

22. Toothpick Bridges 100 toothpicks.
Green glue (no larger than a pencil eraser in diameter anywhere).
Must cross the West River on the bridge tester.
Must be wide enough to allow a Hotwheels car to drive across it.
Must be a TRUSS bridge.
The center of your bridge must allow a bolt to pass through it.
Will be tested with 5, 10, 15, 20, 25, and 30 lb. weights.
5 lbs. earns you a C. 10 a B. 15 a B+. 20 an A. 25 an A+ and 30 lbs is 10 pts. Extra credit.
Good luck!

23. BUT FIRST!
Arch Bridge Challenge!