I-beams, named for their distinctive ‘I’ shape, are structural beams that simplify the construction process by providing excellent load-bearing capacity. Over the years, the I beams have been prompted at customised sizes and specifications on project needs. They are integral in high-rise buildings, offering configurational stability while reducing the need for thick walls and columns for support.
I-beams are widely used as supporting members in the construction of bridges, skyscrapers, parking garages, hospitals, and more. They can handle dynamic loads such as traffic and environmental stresses. This article provides an overall explanation of I-beam types, manufacturing processes, applications, and key features, as well as their advantages and disadvantages.
How Does an I-Beam Work?
As its name suggests, it resembles the capital letter “I” in shape. In a diversity of dimensions and specifications, I beams are created to meet the specific structural needs of buildings. They are also known as universal beams for their wide range of construction applications. These beams are used in frames and vital support elements.
The five main factors involved in the resisting property of the I beam are as follows:
- Bending: When subjected to a load, an I-beam experiences both tensile (stretching) and compressive (squeezing) forces. These forces combine to create a bending moment. When the beam’s yield limit exceeds these forces, the beam may deform and fail to bear more load. I-beams are designed to resist bending through the distribution of material in the flanges, where most of the stress occurs.
- Buckling: Buckling occurs when compression causes a sudden change in the shape of the beam, potentially leading to collapse. The I-beam’s flanges help prevent buckling by adding lateral stability, especially when used as columns in vertical loads.
- Deflection: The degree to which the beam is about to bend to its applied stress or under load is called deflection. It is influenced by the beam’s length, material, and load distribution. Increasing the thickness of the steel or adjusting the beam’s depth can minimise deflection.
- Tension: Tension refers to the pulling or stretching forces that act on the beam’s lower flange during bending. They can be avoided by choosing the right thickness of the web and flanges.
- Vibration: Some usage of external machinery like engines, pumps, and compressors may cause vibration in the construction site. Using I-beams made from stiff steel with higher mass helps reduce the impact of these vibrations, enhancing stability in the construction.
I-Beam Sizes and Classification
I-beams are classified based on factors such as their support, geometry, and cross-section. The I beams are classified into horizontal and vertical beams depending on the position of the flange beam. I-beams are manufactured based on three factors: various steel grades, different sizes such as depth, flange thickness, width, and web thickness, and different shapes (S, W, H, or I).
The standard I-beam steel grades are determined using their yield strength and tensile strength, Which are the minimum and maximum strengths applied to test the grade quality of the steel. The commonly used steel grades are as follows:
- A36: 250 MPa (approximately 36,000 psi).
- A572: The commonly used grade has a yield strength of 345 MPa (50,000 psi), with a range from 290 MPa (42,000 psi) to 415 MPa (60,000 psi).
- A588: This grade can also be used as an alternative to A572.
- A992: Yield strength ranging from 345 MPa (50,000 psi) to 450 MPa (approximately 66,000 psi).
I-Beam Size Chart:
I-Beams are available in different sizes for different applications. The size of the I beam is based on the dimensions and sizes required for the project.
| Standard size | Flange length | Web length | Web thickness | Flange thickness | Weight |
| 800x300x14x26x12m | 800 | 300 | 26 | 14 | 2520kg |
| 900x300x16x18x12m | 900 | 300 | 18 | 16 | 2880kg |
| 600x200x11x17x12m | 600 | 200 | 17 | 11 | 1272kg |
| 588x300x12x20x12 | 588 | 300 | 26 | 14 | 1812kg |
| 500x200x10x16x12m | 500 | 200 | 16 | 10 | 1075kg |
| 200x100x7x10x12m | 200 | 100 | 10 | 7 | 312kg |
| 250x125x7.5×12.5x12m | 250 | 125 | 12.5 | 7.5 | 457.2kg |
| 300x150x10x16x12m | 300 | 150 | 16 | 10 | 786kg |
| 400x150x10x18x12m | 400 | 150 | 18 | 10 | 864kg |
Types of I Beam
I-beams have two horizontal planes referred to as flanges, joined by a vertical element called a web. The cross-section of the I-beam is taller than the wide flange. The most common three types of I-beams used in the construction industry are as follows:
Lightweight I Beams
They are lightweight and often used in construction projects such as low-rise buildings and structures. With their web and flanges, they provide support and stability to the structure. They are cost-effective due to their lightweight nature.
Universal I Beams
The “I” design in the beams allows them to provide sturdiness for heavy load-bearing structures such as bridges and high-rise buildings. The vertical-shaped web is the main load-bearing component, whereas the horizontal shape of two flanges provides support to the structure. They are unique in providing unidirectional bending moments parallel to the web.
Wide Flange I Beams
I beam doesn’t have wide flanges, but it is tapered and narrower than the web, which acts as base materials for bridges and frames.
Applications of I Beams in Construction
- I-beams have a high load-bearing capacity, which reduces the need for excessive steel usage while maintaining structural integrity. Its flexible and stable nature makes it a good choice for every contractor and engineer.
- The web components in I-beams are responsible for withstanding shear stresses.
- Flanges resist bending with their unidirectional bending behaviour.
- Excessive usage of steel can be avoided due to I-beams load-bearing capacity.
- With their wide range of usage and availability, they are considered economical for the construction process.
Advantages of I Beam
- I beam is frequently used in building commercial structures that do not rise above a few heights.
- They are economical and easier to work with due to their lightweight and smaller footprint.
- It can handle the loads effectively from top to bottom of the beam.
- For smaller construction jobs, these i-beams are used to support a span of up to 33 to 100 feet.
Disadvantages of I Beam
- Torsional resistance: I-beams are less suitable for resisting the twisting effect due to their sloped flanges.
- They are effective for building only small-scale construction projects.
Key Features of I Beams
- Shape: It has a cross-section that resembles the shape of the capital letter “I”.
- Web: The vertical cross-section of the beam is considered a web.
- Flanges: The horizontal component of the beam is called a flange. There are two flanges available in each beam.
- Strength: They are solid in providing bending and shear stress.
- Weight Distribution: They provide ideal bending resistance where the top and bottom of the beam bear the load.
I-Beam Manufacturing Process
The production of i-beam involves several processes. They are as follows:
- Preparation of Raw Material
Iron ore is the chief raw material for the production of I-beams. Molten iron is produced from blast furnaces of iron ore with coke and limestone. Meanwhile, scrap metal is sourced from different sources.
- Steel Making Process
In a basic oxygen furnace (BOF), pure oxygen flows at high rates to oxidise the impurities from molten iron. In an electric arc furnace (EAF), the steel scraps are loaded in a furnace and an electric arc is generated to melt to scraps.
- Continuous Casting procedure
By continuous casting, the liquid steel is converted into a semi-finished product which is a raw material for further process.
- Rolling
The semi-finished products are then reheated and passed into the rolling mills which have multiple stands to shape into the desired steel shape.
- Cooling and Straightening
The i-beams are then cooled using the cooling method and straightened to get the desired shape of the steel without any bending.
- Cutting and Inspection
Finally, they are cut into the required lengths.
Conclusion
In conclusion, I-beams are suitable for supporting small construction projects that need to support long-distance spans with significant bending resistance. The manufacturing process is also simple in that it may not need more steel for producing I-beams.