Bridges

1. Bridges

3. Some Local Bridges

12. Beam Bridges

13. Beam Bridge • consists of a horizontal beam supported at each end by piers. The weight of the beam pushes straight down on the piers. The farther apart its piers, the weaker the beam becomes.

14. Beam Bridge: Forces • When something pushes down on the beam, the beam bends. Its top edge is pushed together, and its bottom edge is pulled apart.

15. Continuous Span Beam Bridge • several beam bridges can be linked together, creating what is called a continuous span. Chesapeake Bay Bridge-Tunnel

16. Moveable Bridge • has a deck that moves. • A swing bridge has a deck that rotates around a center point; • a drawbridge has a deck that can be raised and lowered; • a bascule bridge deck is raised with counterweights like a drawbridge; • the deck of a lift bridge is raised vertically like a massive elevator.

17. George P. Coleman Bridge – A Swing Beam Bridge

18. Truss Bridge

19. Truss Bridge • consists of an assembly of triangles. Truss bridges are commonly made from a series of straight, steel bars. Complex Truss Bridge - Cantilever bridge - Firth of Forth Bridge, Scotland

20. Truss Bridge: Forces • Every bar in this cantilever bridge experiences either a pushing or pulling force. The bars rarely bend. This is why cantilever bridges can span farther than beam bridges.

21. Arch Bridge

22. Arch Bridge • has great natural strength. Thousands of years ago, Romans built arches out of stone. Today, most arch bridges are made of steel or concrete. Ancient Roman aqueduct Segovia, Spain

23. Arch Bridge: Forces • The arch is squeezed together, and this squeezing force is carried outward along the curve to the supports at each end. The supports, called abutments, push back on the arch and prevent the ends of the arch from spreading apart.

24. Suspension Bridge

25. Suspension Bridge • can span 2,000 to 7,000 feet -- way farther than any other type of bridge! Most suspension bridges have a truss system beneath the roadway to resist bending and twisting. Golden Gate Bridge -San Francisco

26. Suspension Bridge: Forces • In all suspension bridges, the roadway hangs from massive steelcables, which are draped over two towers and secured into solid concrete blocks, called anchorages, on both ends of the bridge. • The cars push down on the roadway, but because the roadway is suspended, the cables transfer the load into compression in the two towers. The two towers support most of the bridge's weight.

27. Forces on Suspension Bridge

28. Suspension: Cable-stayed bridge • The cable-stayed bridge, like the suspension bridge, supports the roadway with massive steelcables, but in a different way. The cables run directly from the roadway up to a tower, forming a unique "A" shape. Sunshine Skyway Bridge, Florida

29. The Bridge Challenge!

30. The Bridge Challenge • Welcome to Craggy Rock!You got here just in time. This growing community needs four new bridges, and they're very picky about what they want!

31. Bridge Challenge • Test your engineering skills and try to match the right bridge to the right location. • You may use each bridge type only once -- that's a direct order from the mayor of Craggy Rock. Good luck!

32. What Types of Bridge can you choose from? • Truss • Suspension • Beam • Arch

33. Location 1: Multi-lane bridge for commuters and tourists • Location 2: Footbridge across a stream • Location 3: Highway bridge across a busy shipping port • Location 4: Railroad bridge in a national park

34. Location 1:Build a multi-lane bridge for commuters and touristsSpan: 2,000 feetCrossing: RiverConnects: City and major highway • Special Notes:"I want a one-of-a-kind bridge that will span our beautiful river and welcome visitors from all over the world to our thriving city. Make sure the new bridge leaves enough room for sailboats on the river. Please don't build a bridge that looks like the Golden Gate Bridge in San Francisco or the Brooklyn Bridge in New York."-- Mayor of Craggy Rock

35. Suspension Drawbridge Beam Arch What kind of bridge should you build?(Select one)

36. Location 1: Drawbridge • A drawbridge is the best choice for this location. Drawbridges, like the Tower Bridge in London, England, can be quite majestic. They're also practical because they open to allow the passage of boats and ships. The mayor is delighted with your selection!

37. But there is a problem!!!

38. Convenience & Beauty!! • In one of the rowdiest town meetings ever, the residents of Craggy Rock spoke out against the new drawbridge. "It's ugly," one angry resident said, "and there's always traffic on the bridge. They open it for boats, but what about us? We have to get to work, too!"

39. Which bridge will you choose? • The mayor is begging you to build a new bridge. The local steelworkers are on strike, so she advises you to build a bridge with as little steel as possible. Cantilever Bridge Combination: Arch and Beam Cable-Stayed Bridge

40. Cable-Stayed Bridge • Great Choice! It is one of the most popular bridge types in recent years. The roadway hangs from cables like a suspension bridge, forming a unique "A" shape. The mayor is happy because the bridge is made mostly of concrete, a relatively cheap material. The residents are thrilled because ships can pass beneath the bridge without causing traffic jams!

41. Location 2:Build a bridge for rollerbladers and bikersSpan: 100 feetCrossing: StreamConnects: Two bike paths • Special Notes:"We're tired of getting bumped off the road by angry drivers! We want a simple bridge -- one that will connect the bike paths in East and West Craggy Rock over the city stream. We don't have much money, so we're not asking for much. We just want to get to work every day without risking our lives!"-- Craggy Rock Bike-n-Blade Coalition

42. Suspension Drawbridge Beam Arch What kind of bridge should you build?(Select one)

43. Location 2: Beam Bridge • This is an excellent spot for a beam bridge. Beam bridges typically span up to 250 feet, and they're also the cheapest and easiest bridges to build. Congrats -- you've just made a lot of rollerbladers and bikers very happy!

44. But there is a problem!!!

45. Flash Flood! • When it rains, the city stream rises. A really strong storm could cause flash floods, turning the stream into a raging river. Piles of rocks and a wall of gooey mud could push on the piers of the concretebeam bridge and cause it to topple. Luckily, you can fix it before that happens!

46. How will you build a new, flood-proof bridge? Build a higher deck? Build deeper piers? Use stronger material?

47. Deeper Piers • Good Idea!! One of the best ways to strengthen a bridge in a flood zone is to set the piers deeper into the ground. The deeper the piers are lodged into the ground, the harder it is to knock them over. The next time floodwaters pound on the piers of your new bridge, it probably won't budge!

48. Location 3:Build a highway bridge across a busy shipping portSpan: 5,000 feetCrossing: Ocean bayConnects: Island and mainland • Special Notes:"Our records indicate that more than 500 ships pass through Craggy Rock Harbor each day. Please build a bridge that does not block the flow of water traffic. We do not want angry sailors or congestion of any kind in our harbor. Thank you."-- The United States Coast Guard

49. Suspension Drawbridge Beam Arch What kind of bridge should you build?(Select one)

50. Location 3: Suspension Bridge • This is an ideal location for a suspension bridge. Suspension bridges, like the Akashi Kaikyo Bridge in Japan, can span great distances and still leave room for passing ships and boats. The U.S. Coast Guard is thrilled with your selection!