Bridge Building

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Bridge Building

Bridges are consructed to help us go over a river, chasm, road, or the like.

The Basic Bridge Types
Girder Truss Rigid Frame	Arch Cable Stayed Suspension

http://www.matsuo-bridge.co.jp/english/bridges/index.shtm

Step #1 Planning = Let's find an area that needs a bridge.

Click on Google Earth- Let's fly around the plant and look for a river chasm or road that looks like a bridge should be constructed their to help the people in the area.

a. What Latitude and Longatude is your area located at?

b. What types of materials should you construct your bridge out of?

c. Is there an easy way to get the materials to the site?

#2 Making reasoned choices...

Which Type of Bridge is the best suited for your area?

Study each type and then decide the kind of bridge you wish to construct.

The biggest difference between the types pf bridges is the distances they can cross in a single span. A span is the distance between two bridge supports, whether they are columns, towers or the wall of a canyon.

Types of Bridges

http://www.matsuo-bridge.co.jp/english/bridges/index.shtm

Bridge types, construction, and erection

http://www.bardaglea.org.uk/bridges/bridge-types/bridge-types-intro.html

http://library.thinkquest.org/J0113129/DB~1.HTM

http://www.pbs.org/wgbh/buildingbig/bridge/basics.html

Which Bridge Goes Where?

Try the interactive at

http://edsitement.neh.gov/PersianBridge_flash_page.asp

http://www.pbs.org/wgbh/nova/bridge/build.html

#3 How do we Build them?

Check Out the timeline of the Brooklyn Bridge

What important things do we need to consider?

Bridges need to deal with the important forces called compression and tension. Compression is a force that acts to compress or shorten the thing it is acting on.. Tension is a force that acts to expand or lengthen the thing it is acting on.

What stressed acted upon this bridge that made it fail?

Close up Structure

http://pghbridges.com/basics.htm

http://www.bardaglea.org.uk/bridges/bridge-types/bridge-types-suspension.html

#4Building Virtual Bridges

Watch the video above. It shows examples of the bridge building program-

Download the game below and construct bridges the train can cross

Bridge Building Game

Bridge Building Game is a game where you build bridges.

Windows Download (239 KB)
Linux Download (52 KB)
Mac Download (1086 KB)

Using the Westpoint Bridge design software you are going to build your own bridge and load test the structure.

http://bridgecontest.usma.edu/ -this is a free download if you want to practice at home.

http://www.newbaybridge.org/classroom/engineeringfor.html

Construction Tips

Try to keep design simple, using multiples of triangles. An inverted triangle is more stable than a triangle with the apex on top.

Hot glue tends to cook and melt the ends of the spaghetti, so use just enough to hold pieces together.
The bearing points are the points where the bridge is supported at the ends by the edge of the gorge. This area should be flat and smooth. If the bearing point is not flat, the bridge may twist and break.
Spaghetti may be stranded together like a cable or rope.
Spaghetti is brittle and is quite strong in axial tension but very weak in compression. The hint here is to make the compression members as short as practical, by adding internal web members.

Try to make the spaghetti connections strong but flexible. If the connections are too rigid, when the bridge starts to deflect, the joints will twist and rotate and put added bending force into the spaghetti. Spaghetti is not very strong in bending! In fact, if the ends of the spaghetti are cooked and weakened at the joints, then the bending forces from the joint twisting will break the spaghetti very quickly.
Some people have tried boiling the spaghetti for 25 minutes and then slowly drying it while drawing the spaghetti to a longer and more slender dimension. The result is a spaghetti member that is very flexible, light in weight yet quite strong in tension. It is said this process makes for a good tension member but a terrible compression member!

Tips During Loading

Select a maximum of two people from your group to add the load. Try to predetermine the approximate load your bridge will carry. The ratio of maximum load divided by bridge weight is important. The record holding bridge from Camosun College’s Civil Engineering Technology program held almost 90 times its own weight! This bridge used hollow tubes constructed of spaghetti for the compression members. The following tables show the current records for each division:

Division	Record Load Ratio
Up to and including grade 10	26.6
Grades 11 and 12	40.6
Technology students	86.3
Professional	97.4

Apply the load gently, in suitable increments that are not too big, yet not too small either – it’s nerve wracking! Use the heaviest weight increments first.
Try not to unload then reload, this causes joints that have rotated to re-adjust and often the bridge fails sooner than expected.
Keep hand and feet out of the way of falling bridge and weights. Some bridges collapse slowly, while others disintegrate without much warning (but high drama).

Smart Bridges

In this video segment adapted from NOVA scienceNOW, learn about engineering innovations that could help detect a bridge's structural weaknesses before they become dangerous.

Google Sketch Up