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Beam Bridges, Simple but Strong

Beam Bridges, Simple but Strong

  Secondary | Structures | Views: 1400

You will Need:

Two stacks of books to make your ‘abutments’, or even some boxes/packaging

Thick cardboard – such as from cardboard boxes from deliveries, a few pieces of roughly the same size would be helpful, they need to be longer than they are wide

Some weights or heavy items – food tins for example.

What to Do:

  1. Place your stacks of books/boxes around 50-60 centimetres apart, or as far apart as your length of cardboard can reach.
  2. Place one of your pieces of cardboard across your abutment books/boxes. You now have a beam bridge.
  3. Start adding some mass to the bridge: this could be whatever you have laying around that you can build up to make a heavier mass. Weigh and record the weight of each item you add to make sure you know how much weight your bridge can hold!
  4. Add weights until your beam bridge ‘fails’. This is when it collapses or bends so much in the middle it cannot carry any more weight and almost touches the ‘river’ beneath.
  5. What do you notice about how your bridge failed? Did it create a straight line or crease, called a ‘hinge’ in the cardboard? What condition is the beam in after failure? Can you test your ideas, and your bridge again?
  6. Repeat your test again with some new cardboard. Do you notice any difference in how much weight it can hold before it collapses? If so, is there anything different about the cardboard? Why do you think it behaved differently?
  7. Try again with another piece of cardboard, this time adding an arch support underneath (see picture). Add your weights again. What do you notice this time?

Did you find a difference in how the cardboard behaved depending on which way the corrugation ran in the cardboard? Can you see the grooves/lines inside the cardboard? That is the corrugation…Which way tended to be stronger?

Transverse – across the cardboard Longitudinal – along the length of the cardboard

For further details on this activity from the Rochester Bridge Trust, click here

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