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Lesson 1A: Paper Columns:
Working in teams of 2:
Using up to 5 sheets of office paper and a foot of masking tape, make a structure that will support a load of at least two cement bricks( or other heavy load such as Lego EV3 boxes) 8-1/2" off the table.
Minumum Load:12 batteries or 2 bricks
Observe how the structures fail.
Shorter columns fail in compression
Long(slender) columns- fail in buckling
Thus for a given amount of material, a hollow column is less subject to buckling, as it has a greater cross-sectional area.
Euler Buckling: Critical load depends on length, stiffness, and cross-section of column.
When properly designed and loaded, a column (or grouping of columns) is able to support a lot of weight because it transfers it directly to the ground. A column can fail in two basic ways. A load placed off center subjects the column to bending, or buckling. To prevent this, it is important to center a load squarely over the middle third of the top of the column. The second kind of failure occurs when the maximum strength of a column's material is exceeded by the weight of the load. When this happens, the column crushes, or collapses.
Columns are characterized by the stress( force/unit area)Â and strain( change in length) they are subjected to under load.
Try making columns of other materials:
1 liter of dry sand
1 liter of wet sand
1 stick of cold plasticine
1 stick of warm plasticine
1 cubic foot of dry powder snow
1 cubic foot of damp snow
Dry plaster
Wet plaster
Notice how the stress-strain properties of these materials change with their composition or temperature
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