Bridge Designs and Materials 1

Name / Date
Science / Class

Bridge Designs and Materials

Four Classic Bridge Designs / / How These Designs Handle Forces of Tension and Compression /

Part 1 Four Structural Designs

Engineers have learned to work with nature as much as possible when dealing with the tremendous forces and loads that bridges need to handle. To that end, we have created many styles of bridges, each with its advantages and disadvantages. Find out more about four bridge designs—beam, arch, suspension, and cable stayed. Go online to Click on Build a Bridge/ Survey the Four Sites/ Do Your Homework/ Play the Game. In the spaces below, identify each type of bridge structure based on clues about its cost, useful span, and how it supports a load.

cost / 1. / Choose this bridge for low cost and simplicity.
2. / Choose this bridge as a cost-effective solution for medium spans, between 500 and 2,800 feet.
3. / Choose this bridge when you need to, but it will cost the most.
useful span / 4. / This design is typically used for rather short spans (200-800 feet), but it can be made slightly flatter for longer spans. It requires strong end supports to maintain its shape.
5. / This design is used for the longest spans, often between 2,000 and 7,000 feet.
6. / This design is best for medium-length bridges, spans that are less than 900 meters. Otherwise, its towers would have to be too high.
7. / This design is not well suited to spans that require clearance below them (e.g. passing ships).
support for loads / 8. / Supports are required every 250 feet or so. Under a load, the top side of this bridge is compressed, while the bottom side is in tension.
9. / Loads change the downward force of gravity into a sideways push. The weight is carried along the curve to the abutments at the sides, and into the ground. This creates a lot of compression, but little tension.
10. / Towers bear the load. The roadway hangs from cables, forming a unique “A” shape.
11. / The load pulls down on the hangers, which pull on the cables, which pull on the towers and anchors. All these parts are in tension. The towers and their foundations are compressed.
Check out the following links to do more.
12. / This type of bridge is relatively light and flexible. There have been disasters, like the Tacoma Narrows Bridge in 1940, when the wind and the solid support girders caused this bridge to twist and snap in two. Watch it happen at Now, bridges of this type can be stiffened and supported with open trusses that let the wind blow right through.
13. / In ancient times, the Chinese master Li Chun was asked to build a stone bridge over a wide river. The river flowed very fast, and flooded from time to time. Boats had to be able to sail under it. The Anji bridge that he designed still stands 1,400 years later. He incorporated holes in it to lessen its weight, to distribute the compressive forces, and to allow flood waters to flow through the bridge instead of against it. See it at The following video explains more about this ancient shape: (5:41min)
14. / This type of bridge is optimal for medium distances, and stiff enough to resist deforming under live loads and earthquakes, It can be built quickly because it does not require anchorages, and ituses fewer materials than a concrete structure. On the other hand, this type of bridge but may rock from side to side in windy areas, and it requires a lot of repair and maintenance because its cablescorrode. The tallest bridge in the world is this kind, and it was built to last 120 years. Optional: Watch a documentary of how the Millau Viaduct was built at (46 minutes).
15. / Some bridges combine features from different styles. The Hangzhou Bay Bridge in China combines two styles. View it at and decide.

Part 2 Bridge Materials

The ideal material for making a bridge is able to handle compression and tension forces, it lasts well in outdoor conditions (wind, salt, temperature changes), and it yields or deflects when under stress before failing,as opposed to breaking without warning. The ideal material is also inexpensive, available, and easy to work with. Materials that people have used to make bridges include wood, stone, wire, iron, plastic, rope, concrete, and steel. No single material has all the ideal characteristics. Most often, different parts of a bridge use different materials. For example, concrete may be used for foundations, while steel might be used for beams and cables. Also, materials may be combined. For example, steel may be embedded in concrete to give a bridge part the advantages of both materials. Steel and concrete are currently the two most popular materials for making heavy-duty bridges for vehicle and train crossings. Research and find two advantages for each material, and two disadvantages for each material.

  • Steel: Steel is a mixture of iron, carbon, and other materials.

16. Advantage:
17. Advantage:
18. Disadvantage:
19. Disadvantage:
  • Concrete: Concrete is made of cement plus water, sand, and gravel. Cement mixed with water creates a chemical reaction called hydration that causes the cement to harden.

20. Advantage:
21. Advantage:
22. Disadvantage:
23. Disadvantage:

Part 3 Build an Arch Bridge

Goal
Criteria
Constraints
Roman aqueducts, built over 2,000 years ago.
/ Arc de Triomphe, Paris, France, completed 1836.

Wushan Yangtze River Bridge, China, completed 2005
/ The Landwasser Viaduct Switzerland, completed 1902

Sources

"Bridge Design and Construction Statistics."Golden Gate Bridge. N.p., n.d. Web. 09 Feb. 2017.

"Encarta_bridge."Encarta_bridge. N.p., n.d. Web. 12 Mar. 2017.

"Facts and History of Rialto Bridge."Rialto Bridge - Facts and History of Ponte Di Rialto. Bridges Database, n.d. Web. 09 Feb. 2017.

"Operation Build a Bridge and Get over It - Activity.". N.p., n.d. Web. 12 Mar. 2017.

"Painting the Golden Gate Bridge."Golden Gate Bridge. N.p., n.d. Web. 09 Feb. 2017. <

"Strength of Materials - Lesson.". N.p., n.d. Web. 09 Feb. 2017.

Materials
Plasterboard (60cm X 6.5cm X 7.5cm)
Styrofoam (122cm X 2cm X 19cm)
_____ large popsicle sticks
5 meters String
5 pipe cleaners
Cardboard
All-Purpose Joint Compound (water-based)—the class will share a 3.5 quart tub)
Text books (no damage / Criteria
1. the bridge can combine any of the four main styles, but it has to incorporate arches in a functional way.
2. any height
3. minimum width = 12cm
4. minimum span = 50cm
5. minimum strength = model car with added 1000gm weight
Constraints
Finish in 5 classes
Use only materials provided in class