Types of Beam Structures and their Applications in Construction

A strong structural frame is essential for the safety and stability of any building. Beam structures form a critical part of this load-bearing system. Beams are the horizontal members that support the immense weight of floors, roofs, and walls. They carry these heavy loads over to the columns and then down to the foundation.

For any homeowner, having a basic understanding of the different types of beams is very useful. This guide provides a comprehensive overview of the common beams used in house construction, explaining how they are supported and where they are used.

What is a Structural Beam?

A structural beam is a horizontal support. It is designed specifically to carry weight. Its main purpose is to resist forces that try to bend it from above.

You can think of a beam as a bridge. This bridge carries the load of a slab or a wall across an open space to the vertical supports.

These supports are usually concrete pillars or strong walls. The correct design and placement of every single beam is fundamental to the safety of your home.

Beam Types Based on Support Conditions

The way a beam is supported is the primary way to classify it. This support system defines how the beam carries its load.

• Simply Supported Beam

This is one of the most common and basic types of beams.

A simply supported beam rests on two supports, with one at each end.

The beams that you often see running across a room, resting on a wall on either side, are good examples of this type.

• Cantilever Beam

You have probably seen cantilever beams in your daily life. They are used to create balconies or unsupported roof projections.

This beam is firmly fixed at only one end.

The other end juts out freely into space. This unique design creates special kinds of stress. For this reason, it must be carefully designed by a qualified structural engineer.

• Overhanging Beam

An overhanging beam is a combination of a simply supported beam and a cantilever beam.

It is supported at two points, but one or both ends extend beyond the supports. The part of the beam that extends past the support acts like a cantilever.

• Continuous Beam

A continuous beam is a single beam that extends over more than two supports. You will often see this design in larger buildings.

A single long beam might run across several columns in a row. This makes the entire structure more rigid. It can also be a more efficient design than using several separate beams.

• Fixed Beam

A fixed beam is supported rigidly at both ends.

Unlike a simply supported beam, these supports prevent any rotation or movement.

This rigid connection makes the beam very strong and stable. You will find this type of beam in structures where high stiffness is required to minimize deflection.

Beam Types Based on Placement and Function

Beams are also named based on where they are placed in a building and what specific job they do.

• Plinth Beam

The plinth beam is a crucial beam built at or just above the ground level.

It connects the foundation of the house to the walls above it. It has two very important jobs.

First, it distributes the load from the walls evenly across the entire foundation.

Second, it helps to prevent dampness from the ground from rising up into the walls of the house.

• Lintel Beam

This is a very common beam. This is also very important from the earthquake resistance point of view. The lintel beams should preferably run across full length the walls.

A lintel beam is placed directly above openings in a wall, such as for doors and windows. Its purpose is to support the weight of the brickwork or concrete wall above the opening and if designed properly, they may also help in Earthquake resistance

• Grade Beam

A grade beam is similar to a plinth beam. It is a reinforced concrete beam that rests directly on the ground or is supported by piles.

It is often used in areas with poor soil conditions to provide a stable foundation for the walls above.

• Tie Beam

A tie beam is a horizontal beam that connects two columns or roof trusses. Its main purpose is not to carry vertical weight from a slab.

Instead, it acts as a tie to hold the columns together and prevent them from spreading apart or buckling.

• Spandrel Beam

A spandrel beam is located on the outer perimeter of a building.

It is positioned at each floor level to support the exterior wall and the edge of the floor slab. You often see this type of beam in multi-story buildings.

• Hidden or Concealed Beam

This is a special beam that is hidden within the depth of a concrete slab. It does not project downwards below the ceiling level.

Architects use a hidden beam when they want to achieve a completely flat ceiling without any visible beam obstructions.

Beams based upon Cross Sectional Shape

1. Rectangular Beams – These are very basic and common with simple rectangular shape. They support bending & compression loads and widely used in residential & high rise buildings

2. I Beams or H Beams – These beams have “I” or”H”shape, with two horizontal flanges connected by a vertical web. They provide high strength to weight ratio and excellent bending resistance, making them ideal for bridges, buildings and other large structures.

3. T – Beams – They are often constructed as a single unit with slabs in floors & roofs. The top flange is effective in resisting compressive stresses and web resist the shear stresses.

4. Hollow Box Beams – These are hollow and consist of two horizontal & two vertical plates forming a box shape. They offer exceptional torsion resistance and are used in heavy duty applications like box girder bridges, large span roofs and culverts.

Frequently Asked Questions (FAQs)

Which type of beam is best?

There is no single best type of beam.

The most suitable beam structure depends entirely on the building's specific design. Factors include the length of the span it needs to cover and the load it must support.

A structural engineer is the professional who decides the most appropriate type of beam for each location.

What is a plinth beam?

A plinth beam is a reinforced concrete beam. It is constructed at the plinth level of a building, between the foundation and the ground floor wall. Its purpose is to distribute wall loads and to act as a barrier against ground moisture, if properly casted. All the plinth beams well tied together offers great earthquake resistance.

What is the minimum height of a plinth?

The minimum height of a plinth above the surrounding ground should generally be between 300mm and 450mm. This is about 12 to 18 inches. This elevation helps to protect the house from rainwater and dampness.

What is cantilever in beam?

A cantilever in beam refers to a beam that is supported only at one end, while the other end extends freely without any support. This design is commonly used for balconies, porches, and unsupported roof overhangs.