Cantilever:
A cantilever is horizontal, like a beam, but is supported only at one end. A tree branch is an example of a natural cantilever. A cantilever can be either a single beam or a wide slab. One of the most famous buildings made with cantilevers is Fallingwater (top left slide), by Frank Lloyd Wright, which was constructed by projecting a series of reinforced concrete slabs out over a waterfall in the Pennsylvania woods. Reinforced concrete has steel rods inside it that can withstand tension and prevent the concrete from sagging or cracking under the load.
A cantilever bends downward like a beam, but a beam bends in the middle and a cantilever bends at the unsupported end. When a cantilever bends, the top gets stretched and the bottom gets compressed. (Slide, not shown here.) This bend is so slight in rigid materials that you can't see it, but imagine a diving board with someone standing out at the end, making it dip down toward the water. A diving board is a cantilever that's supposed to be flexible, so it gives you an exaggerated look at the way a cantilever responds to a load.
When you pull open a drawer, it becomes a cantilever supported by the weight and rigidity of the cabinet. The opened drawer can support a heavy load as long as the cabinet is heavy enough for gravity to hold it firmly in place. A balcony (bottom left slide of Mykonos, Greece) is a cantilever, too. Although you may see brackets that add support or decoration below it, a balcony stays in place because part of it extends back into the wall of the building in the same way that a drawer extends back into the cabinet.
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AIE is a program of the AIA Philadelphia Chapter
Structure in Architecture and the AIE Web site: Copyright 1999 Foundation for Architecture
AIE is a program of the AIA Philadelphia Chapter
Structure in Architecture and the AIE Web site: Copyright 1999 Foundation for Architecture