What is a Cantilever?
A cantilever is a structural element that extends horizontally beyond its support, with one end fixed and the other free.
Definition
Purpose
Cantilevers are used by architects and engineers to create open, usuable spaces without the need for columns or supports under the projecting portion of the structure. This proves helpful when designing balconies, roof overhangs, canopies, walkways, and other features that extend beyond a building's main footprint.
They also offer greater design flexibility, using which structures can stretch out while maintaining a clean appearance. The supporting structure should, however, be designed to handle the bending forces and loads created by the cantilever.
Examples of Use
- Balconies: A cantilevered balcony extends outward from a building, but does not have columns supporting its outer edge.
- Roof overhangs: Cantilevered roof sections extend beyond exterior walls to provide shade and also keep rainwater out of the building.
- Canopies: A cantilevered canopy projects over an entrance or walkway without requiring support columns at the front.
- Bridges: Cantilever construction enables bridge sections to extend outward from piers, which can even allow construction across wide spans or difficult terrain.
- Staircases: Cantilevered stairs are anchored into a wall or structural support, and thus create a floating appearance without visible supports beneath each step.
Notes
- Unlike a simply supported beam, a cantilever is fixed at one end and free at the other.
- The projecting section experiences bending and shear forces, which the fixed support must resist.
- Cantilevers can be built using reinforced concrete, structural steel, timber, or other suitable materials.
- Excessive bending can affect the structure's safety, appearance, and serviceability.
- The longer the cantilever or the greater its load, the more carefully its dimensions, materials, connections, and supporting structure must be designed.
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