Example for cantilever beam is
Portico slabs
Cantilever Beam Definition and Examples
A cantilever beam is a fundamental structural element that is supported at one end only, with the other end extending freely into space. The fixed end of the cantilever beam is typically built into a wall or column, providing rigid support against vertical loads, horizontal forces, and rotational movements. This unique support condition allows the free end to project outward, making cantilever beams suitable for various architectural and structural applications where an unobstructed span is desired.
Key characteristics of a cantilever beam include:
- It has only one end rigidly fixed or built into a support.
- The opposite end of the beam is unsupported or "free."
- Loads applied to the free end or along the span of the cantilever beam create significant bending moments and shear forces, with the maximum values often occurring at the fixed support.
Examples of Cantilever Beams in Structures
Let's analyze each of the given options to determine which one serves as a clear example of a cantilever beam:
| Option | Explanation | Is it a Cantilever Beam Example? |
|---|---|---|
| Railway Sleepers | Railway sleepers (or railroad ties) are placed perpendicular to the rails and are supported by ballast (crushed stone). They distribute the load from the rails to the ground. They are generally considered continuously supported or simply supported members, not cantilevered. | No |
| Portico Slabs | A portico slab is a common architectural feature, often a projecting roof or canopy over an entrance. When this slab extends from a building's wall without any external support (like columns) at its outer edge, it functions as a perfect example of a cantilever beam. The wall provides the fixed support, and the slab projects outwards freely. | Yes |
| Roof Slab | A typical roof slab in a building is usually supported on all four sides by beams or walls, or on two opposite sides. While a portion of a roof might overhang and act as a cantilever, the general term "roof slab" typically refers to a slab supported in a way that is not primarily cantilevered. | Generally No |
| Bridge | A bridge is a large structure designed to span an obstacle. While some types of bridges (e.g., cantilever bridges) or specific components within a larger bridge structure can utilize cantilever principles, "bridge" itself is a broad category encompassing various structural forms (simply supported, suspension, arch, cable-stayed, etc.). It is not as specific an example of a single cantilever beam as a portico slab. | Partially, but not the best general example. |
Identifying the Best Example of a Cantilever Beam
Based on the analysis, portico slabs are a direct and excellent example of a cantilever beam. Their typical design involves being rigidly fixed at one end (to the building wall) and projecting outwards with a free, unsupported end. This structural configuration makes them a classic illustration of a cantilever beam's application in civil and architectural engineering.
Important Questions from Beams
For a simply supported beam or slab, the effective span is calculated as:
Which of the following is CORRECT for indeterminate beam condition?
A cantilever beam is one which is -
In case of deep beam or in thin webbed R.C.C members, the first crack formed is-
In case of web crippling, the dispersion of load from bearing plate takes place at:
