What Is A Cantilever Beam?
A cantilever beam is a rigid structural component that has stability at one end and is unsupported at the other. The cantilever beam may be constructed of steel or concrete, with one end cast or attached to a vertical support. Vertical loads are applied to the horizontal beam construction’s free end.
A cantilever girder in a bridge is made up of a cantilever beam, which is constructed as an addition to a building frame in a structure. It can be constructed utilizing structural cast-in-place or prestressing methods.
Overhanging buildings may be built using cantilever architecture without the need for extra bracing and supports. This structural component may give a building, tower, or bridge a special appeal. It is frequently employed in building construction.
This article describes several crucial structural activities and fundamental cantilever beam fundamentals.
Who Invented Cantilevers?
Cantilevers in architecture are attributed to Frank Lloyd Wright. When Wright built the Robie House in Chicago in 1906, he employed them. The first cantilever bridge across the Main River in Germany was built in 1867, according to German engineer Gottfried Heinrich Gerber.
How Does The Cantilever Function?
Weights are supported above the beam by a cantilever. Cantilevers have no deflection because the upper half of their thickness is put under tensile tension while the lower half is under compressive stress.
A cantilever is a rigid body in which the beam is held in place by the constraints at the fixed end. The cantilever construction doesn’t move because the fixed end counteracts forces at the free end. Steel and concrete are put together to form it.
Cantilever Beam’s Structural Behavior
A cantilever beam bends downward when it is subjected to vertical stresses. A cantilever beam can be subjected to variable load, uniform load, or point load.
Regardless of the weight, it generates an upward concavity and bends downward. This bending causes the upper fibers to be stiff and the bottom fibers to be compressed. Therefore, main reinforcement is provided to the top fiber of the concrete beam due to the significant tensile stress.
Bending Moment (BM) and Shear Force (SF) (BM)
The total loads between a section and the free end make up the shear force at any segment of a cantilever beam. The total of all the moments around a particular segment of a cantilever beam caused by all the loads operating between that section and the free end constitutes the bending moment at that section.
A cantilever beam’s bending moment is greatest at the fixed end and zero at the free end. For each feasible load combination, the bending and shear force diagram is calculated in order to build a cantilever beam for a construction. According to the design guidelines, a mix of dead load and live load is applied to the beam.
Cantilever Beam Design
Under the influence of the structural load, a cantilever beam is susceptible to moment and shear stresses. Any design approach aims to transmit these pressures to the support in a secure manner.
A cantilever beam’s bending moment ranges from zero at its free end to its greatest value at its fixed-end support. Therefore, in the design of cantilever beams, the top fiber of the concrete beam is given the primary reinforcement to safely handle the tensile stress.
A cantilever beam’s maximum span is often shaped by the following variables:
- The cantilever’s depth
- The size, kind, and placement of the load
- The standard and kind of the material utilized
Typically, the span of tiny cantilever beams is limited to 2 to 3 m. However, either by raising the depth or by adding a steel or prestressed structural unit, the span may be expanded. Given that the structure can safely convey the cantilever-generated moments to the ground, the span can be built to be rather long. The possibilities of long-spanned cantilever beams may be researched with the aid of a thorough analysis and design of the structure.
To minimize the effect of overturning, the cantilever beam must be securely fastened to the wall or support.
Cantilever Beam Applications In Construction
Applications for cantilever beam constructions include the following:
- Building balconies and cantilever beams
- Cantilever support structures for the short to medium term
- Without guy-wires free-standing radio towers
- Cantilever beam construction for pergolas
- Building lintel construction
Benefits and Drawbacks of Cantilever Beams
The following are some of cantilever beams’ key benefits:
- Cantilever beams don’t need assistance from the other side.
- Cantilever beams’ negative bending moments serve to balance out the positive bending moments produced.
- Cantilever beams are simple to build.
The following are cantilever beam’s drawbacks:
- Large deflections are applied to cantilever beams.
- Moments are greater for cantilever beams.
- The construction must have a sturdy fixed support or a backspan to remain stable.
Cantilever Beam FAQs:
1. What is the longest span a cantilever beam can have?
Typically, the span of tiny cantilever beams is limited to 2 to 3 meters. However, either by raising the depth or by adding a steel or prestressed structural unit, the span may be expanded. Given that the structure can safely convey the cantilever-generated moments to the ground, the span can be built to be rather long. The feasibility of using long-spanned cantilever beams may be investigated with the aid of a thorough analysis and design of the structure.
2. What behavior does a cantilever beam exhibit when loaded?
When a cantilever beam is under vertical loads, it bends downward. It may be exposed to variable, uniform, or point loads.
Regardless of the weight, it bends downward by generating an upward concavity. The lower fibers are compressed and the top fibers are tense as a result of this bending. As a result, the upper fiber of the concrete beam receives the primary reinforcing during the design of cantilever beams in order to safely handle the tensile stress.
