Last week we played around with the physics involved in Stonehenge, one of the earliest Post and Lintel constructions. Although a technique still in regular use today, Post and Lintel structures have some limitations, mainly in their ability to hold heavy loads and span great distances.
Welcome the arch. Do to their method of construction, arches can actually become stronger under increased pressure (in the case of the a masonry arch), but there are some important elements that make this statement true.
To find out how an arch works we did this little 5 minute experiment with some cardboard arches that we cut from a standard drawing tube.
First we took a singular arch and tested its strength. Easily crushed by a finger and with even more ease by a large garden brick, we observed how a single unsupported arch was in fact not very strong.
Then we tried taping a few arches together to see what would happen....
... and they easily held up the brick! This was because the thrust of each arch was counteracted by the next keeping them from collapsing. In other words, as each arch tried to collapse and push outwards, the arch next to it was trying to do the same thing, so they ended up pushing back at each other, which in turn strengthened the structure. We then tried to add another brick, but since the ends were not supported, the additional weight caused the line of arches to push outwards and collapse.
Next we tried supporting (or buttressing) the ends of the line of arches to keep them from sliding outwards and...
... they easily held up 2 bricks since the thrust was grounded by the heavy and sturdy blocks on the ends.
Simple and quick, this project helped us learn a lot about arches and how they work!
For more simple architectural projects, take a look some of our past experiments:
Sticks and Stonhenge (simple machines and post and lintel construction)