Building Bridges

Many children enjoy experimenting with bridges. In one nursery, the children experimented with building bridges. They started by using some blocks in the classroom and placing model people on top of the bridges. They then progressed to making bridges large enough to walk over themselves. Some images and discussion about this exploration are given below.

A:“They haven’t built it right, look at this! It’s just falling down, down, down all the time.” Teacher:“I wonder if you could help them? How can we make it strong so it doesn’t keep falling down?”
A:“We need bigger blocks at the bottom.”
B:“Yeah, bigger blocks are stronger.”
The children then decided that the bridges were dangerous and needed fixing, they managed to successfully fix the bridge so that one of them could walk across it.
A:“It’s perfectly safe now. I tested it and it didn’t fall down.”

Five photos showing children making bridges in some of the photos, the children walk across bridges they have made out of crates and planks of wood.

Talking with these children more about bridges could lead to some interesting discussions. Some things that the children might find interesting to think about are given below.

Shapes in Bridges

The children might be interested in spotting the different types of shapes used in bridges. Some of the most common are triangles and arches. Triangles are commonly used in construction work due to their strength. To learn more, please see our article on triangles in construction.

Arches are also commonly used in construction, with historical architecture utilising arches in windows, doorways and of course, bridges and viaducts. Arches are a popular choice due to their ability to evenly spread the weight they support. Children might find it interesting to learn about how these arches are built and to have a go at building some for themselves. It could be interesting for them to consider how the arch is not strong and will need to be supported until the last stone (the keystone) is placed. In the image below, there is a sketch of an arch made from blocks.

Investigating the Stability of Bridges

The children could carry out some experiments to see how stable their bridges are. To make this experiment more interesting, the children could use weaker materials to build their bridges and see which is the heaviest item they can hold. To make their bridges stronger, the children could add more supports underneath the bridge to see if this makes a difference. This could be a good opportunity for the children to practice some data collection and visualisation. To learn more, you can see our articles on data collection and types of graphs.

To make bridges out of paper stronger, the children might want to add a folded layer of paper. This folded layer will add additional strength in the same way it does in corrugated cardboard. You can read more about this in our article on corrugated cardboard.

Moving bridges

Some bridges are also able to move, allowing boats to pass underneath them. There are several different ways that bridges can move; some good examples include Tower Bridge in London, the Gateshead Millennium Bridge and the River Tyne Swing Bridge.

Tower Bridge is a bascule bridge where two parts of the centre of the bridge lift up in the middle to allow taller ships to pass through. The Gateshead Millennium Bridge is a tilt bridge; the walkway pivots upwards, and the top of the bridge swings down a little until the two are level. Tilting the walkway allows enough room for boats to pass under the bridge. In the images below, you can see Tower Bridge and the Gateshead Millennium Bridge.

Two images, one of Tower Bridge (sourced from unsplash) and one of the Gateshead Millennium Bridge (sourced from pixabay). In the image of Tower Bridge, the bridge is parted and a ship is passing through.

The River Tyne Swing Bridge is an example of a swing bridge. These types of bridges move horizontally so that a section of the bridge points parallel to the river, and ships can move past. Children could spend some time categorising the types of bridges into groups and thinking about the different purposes of each bridge. Some bridges cross water, and some cross traffic; some bridges transport people, others transport trains, and some bridges let cars and people cross at the same time. Bridges are designed for specific purposes; for example, the River Tyne Swing Bridge could, in theory, allow a ship of any height to pass through, whereas the Millennium Bridge can only let ships of a certain height underneath, as the walkway only lifts up and doesn’t split. Thinking about the similarities and differences between types of bridges and the different categories they can be sorted into might be a fun comparison exercise for children to try.

In one nursery, the children became particularly interested in Tower Bridge and spent some time learning about the mechanisms that make the bridge move and also making their own imitations of the bridge. Some of their comments and models can be seen below.

A: “It’s got a bit that opens and closes”
Teacher: Why does it do this?
B: “To let the boats through”

Three images. In the first image, the children look at pictures of different bridges. In the second is a piece of cardboard a child has folded to mimic the motion of Tower Bridge. In the third image, a child has built a model of Tower Bridge out of wooden blocks.

The children were intrigued by how the bridge worked and so watched some videos of the mechanism. Learning about the engine that powers the bridge led them to start investigating cogs, you can read about this in our article cogs.