STRESSED OUT STRUCTURES

The clay was rolled out flat on a hand-built pottery rolling board then cut out in one-inch squares with a small knife. Some bricks were cut and shaped to make an archway. The bricks were soft so they were put in the oven at 200 degrees F all day. After that they were still crumbly so they were taken to a potter who fired them in her kiln.

Rolling Out the Clay

When they were done, icing sugar was used to mortar the bricks to build the gateway tops but it didn’t work because it was too soft and slippery. Then real brick mortar was used but it still didn’t work because it was too gritty and crumbly. Thinset mortar for tiles was used but it was way too strong. Nothing could break even the flat gateway!

Then play dough was used and that worked. A template was made to help build the gateway tops. The gateway tops were left to dry.

Sand bags were made for weights. First the empty bags were put on the scale and were filled with sand. They were tied together to make pairs of bags that weighed 50, 100, 200 and 400 grams.

To test the strength of each gateway top, they were set on wooden blocks and sand bags were put on the centre stone of the arched and flat gateway tops until they broke. The weight of the bags was added up and recorded in a chart.

For each test, three trials were done.

Results

TABLE ONE - SHAPE OF GATEWAY: Weight to Break (g)
Trial #	Flat Gateway	Arched Gateway
1	300	400
2	200	500
3	400	400
average	300	433

Conclusions

Which gateway is stronger?

It turned out that it took 133g more weight to break the arched gateway than the flat gateway. This is because the stones in the arched gateway lean against each other and the center stone. Weight is transferred to the ground.

To Materials

To Top

To Part Two

1. Arched Gateway

2. Straight Gateway