The following comes from Structures, a 1986 exhibit at the Franklin Institute Science Museum.

Buckling

Push on the ends of a piece of uncooked spaghetti. The sideways bending is called buckling. The compression force that you apply causes complex internal forces that bend the spaghetti sideways. If you push hard enough, it will snap. The snapping starts on the edge where the tension force within the spaghetti is great enough to pull it apart.

Brittle materials like spaghetti, stone or glass break rather easily this way. Stone columns must be made so they won't buckle—because once they start to buckle, they will collapse.

Suspension Bridge

Tie a string between two books. Push down on the string. The "cable" pulls down and inward, toppling the books.

Now set up the books on a board. Pass the string over the books to thumbtack-anchors on the ends of the board. Push down slowly, harder and harder. You'll be able to put a lot of load on the string-cable; you may even be able to push hard enough to lift the thumbtacks out of the board.