Structure Challenge

Image of the final structure challenge item

You will need

  • A packet of jubes or another type of jelly lolly. Cheese cubes or marshmallows can also be used.
  • A box of toothpicks
structure challenge - ingredients

What to do

Using only toothpicks and lollies make a self-supporting structure.

Guidelines for building your structure

  • This activity can either be done in a group or on your own
  • Each group should receive set amount of toothpicks and lollies
  • To finish (or win) the challenge each group should either build the tallest structure possible, the structure that can bear the most weight, a simple structure like a house or a bridge or the structure that most resembles a famous building, for example the Eiffel Tower
  • A time limit for this activity is optional

What shapes are the strongest? Square and triangles are very strong shapes.

How to build squares and cubes

Tto make a square you will need four toothpicks and four lollies. Poke the toothpicks into the lollies to make a square with a lolly at each corner.

Using only toothpicks and lollies make a self-supporting structure

Even though the structure appears still, their parts are always pulling and pushing on each other.

The triangle is the strongest shape.

To make a cube poke another toothpick into the top of each lolly. Put a lolly on the top of each toothpick. Connect the lollies with toothpicks to make a cube.

Structure Challenge - the experiment in action

How to build triangles and pyramids

To make a triangle you will need 3 lollies and 3 toothpicks. Poke the toothpicks into the lollies to make a triangle with a lolly at each point. To make a pyramid poke another toothpick into the top of each lolly. Bend those 3 toothpicks in toward the centre. Poke all 3 toothpicks into one lolly to make a 3-sided pyramid.

For a 4-sided pyramid, you need a square on the bottom and triangles on all 4 sides. Build a square, and then poke a toothpick into the top of each corner. Bend all 4 toothpicks into the centre and connect them with one lolly, making a 4-sided pyramid.

Hint: If you use both triangles and squares in your structure your tower will be less wobbly.

structure challenge in action

What's happening?

Even though the structure appears still, their parts are always pulling and pushing on each other. Structures remain standing because some parts are being pulled or stretched and other parts are being pushed or squashed. The parts that are being pulled are in tension. The parts that are being squashed are in compression.

Strong structures such as towers, bridges and beams have to be able to cope with pushing (compressive) and pulling (tensile) forces. For example, two bricks side by side can withstand pushing forces, but not pulling forces. A rope can withstand pulling forces but not pushing forces. What shapes can you think of that are strong when you push or pull them? Bridges are great examples of structures that use simple shapes for strength.

Triangles form the strongest structure because all three sides bear the load. Compression pushes down equally on two sides of the triangle, causing the base to be pulled equally in two directions, which creates tension. In a square, two sides of the structure bear the load.

Applications

Triangles are used to make a very strong form called a truss. A truss is a type of frame that is designed to be stiff. Before steel, trusses were made of wood or iron. Now they are almost always made of steel, though some concrete trusses exist, and some smaller examples use timber.

Circles are also among the strongest shapes in nature. External and internal stress distributes itself evenly throughout a circular structure. Plant stems and tree trunks are examples of the strength of the circular shape.

A bicycle is also an example of a structure that uses simple shapes for strength. The frame of a bicycle is made up of triangles, the frame is tube shaped and the wheels are circles reinforced with triangles. This makes the bicycle a very strong machine.

The pylons at each end of the arch of Sydney Harbour Bridge are not a structural feature of the bridge. They do not support the arch and were built to enhance the appearance of the bridge.

 

Activity adapted from Science by Email, part of CSIRO's Double Helix Science Club. To Join the Club, with a choice of magazines, weekly email experiments, events and other benefits, visit www.csiro.au/helix or call 02 6276 6643. Subscribe to FREE Science by Email at www.csiro.au/sciencemail