Different Types of Beam- Why cantilever beam are made trapezoidal


What is Beam?

Different types of beam are used in construction as a frame of the structure. The beam is the horizontal structural component that significantly bears loads in the form of bending. Moreover, it transfers the load in form bending forces and horizontal forces to the column and then to the foundation and ultimately to ground strata (bed).

Beam basically support the structure by resisting shear forces and rarely by compression and tensile forces.

Why beam is provided in structure?

The basic functions of beam is to collect all the slab loads within it and manage to transfer all loads to the nearest columns. Moreover, beams also provide the horizontal support and rigidity during seismic action of structure.

Thus beams are designed with necessary reinforcement, a suitable cross-section having a high moment of inertia so that it can well support corresponding slab and load on it.

Types of load on beam

Generally, the beam is executed simply four types of load. That is Point load, uniformly distributed load, uniformly varied load and torsional load.

And on the basis, if the nature of loads that are executed on beam, there are basically, Dead load or a self-weight load of a beam, live load(load that continuously changes its position), seismic load(load caused due to seismic activities) and sometimes wind load.

Types of beam

Types of beam are classified under various categories such as, on the basis of the support provided, on the basis of their structural. Placement, on the basis of their shapes, on the basis of their composition.

On basis of support

The different beam has different types of support to hold the beam. Different types of beam supports have given at the last of this content. Now, let us see different types of the beam.

Simply supported beam:

Beam that has one end roller support and other end hinged support is known as a simply supported beam. This beam is simply kept on the support like a column. It means that it can not resist the horizontal force

Fixed support beam:

Beam that have both end supported to rigid support is known as fixed supported beam. There is no any horizontal or vertical movement in this beam. So, It have shear as well as bending moment at the support.

Continuous support beam:

These beam consist of many support throughout the span composing hinge and roller supports is known as a continuous beam. This beam is generally constructed in residential, hospital, industrial, etc.

Cantilever support beam:

Beam having one end fixed to the rigid support and other end suspended freely is known as cantilever beam. This beam has extended somewhat from its nearest support. You can see in the picture below.

Cantilever beam
Cantilever beam

Why cantilever beam are made trapezoidal?

The beam at cantilever portion is generally made trapezoidal (longitudinal section)  or say the beam cross-section is uniformly reduced to the tip of the cantilever for optimization, as there is no moment at the tip of the cantilever but the existence of shear forces.

Types of beam On basis of shape

  1. Channel section
  2. Rectangular section
  3. I section
  4. T section
  5. Hollow section

On basis of structural placement

Primary beam : The beam that connect two major column to form strong frame structure is known as primary beam.

Secondary beam : Intermediate beam that is connected between two beams is known as secondary beam. It is provided where the span of the slab is larger and it have to cover heavy load.

Plinth beam : Beam  that is just made above ground level to transfer the load of brickwork or wall through the column is known as plinth beam.

Tie beam : Beam that is basically use to tie the footings and column below ground level is known as tie beam. Read detail about plinth beam and tie beam below.

Read Also, Difference between Tie beam and Plinth beam – and their Function

Types of beam on basis of composition

Steel beam: Generally, used in truss and steel structure, the roof structure of steel. Such beam consists of various shapes like I, H, C, hollow, T,etc due to their easy moulding and casting

Wooden beam: Used in traditional houses consisting of mud-mural mortar and As a joist in temples.

Concrete (Reinforced) beams: A most common type of beam especially designed with the placement of the reinforcement bars and stirrups and the grade of concrete as per requirements. Difficult to form various shapes so commonly rectangular section beam is made.

Composite beam: Beam that consists of two or more materials like steel and wood, steel and concrete for better performance.

Material used in beam

The material used in the beam basically depends on the type of beam on the basis of the composition. But most commonly used material in the beam are concrete, reinforcement bars, steel, timber wood, and other synthetic materials.

For the concrete (Reinforced)  beams, the reinforcement bars can be available of different sizes generally cylindrical consisting of some cylindrical or spiral ridges for better cohesion with concrete. And for the concrete, the aggregate selection and type of admixture and cement used depends upon structure type.

For example, the aggregate size used for the bridge’s beam might be different than the aggregate size used for the residential house even though the same grade of concrete is to be made.

Moreover, the beam is sometimes provided with Haunch and called a haunch beam, to reduce the shear in the beam. Haunch is the triangular prismatic shape provided at the edges f beam or slap where there is a sudden change in shape and shear forces.

All Types of Beam Details- Why cantilever beam are made trapezoidal
Haunch beam

For example, the haunch can be used in a beam where there is a different cross-section of the beam throughout its span.

Types of beam supports

I hope this article remains helpful for you.

Happy Learning – Civil Concept

Contributed by,

Civil Engineer – Rajan Shrestha

Read Also,

T beam design – Parts of T Beam with Numerical Calculation

Effective span of beam for simply supported, Cantilever, Continous- IS

Overhanging Beam – Types | Advantages, and Disadvantages

Point of Contraflexure – Zero bending moment at a section of Beam

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