When it comes to structural elements in construction, RSJ beams play a crucial role. RSJ stands for Rolled Steel Joist, and these beams are the main parts of modern building design.
What is an RSJ Beam?
An RSJ (Rolled Steel Joist) beam is a structural steel component commonly used in construction. It has a distinctive ‘I’ or ‘H’ shape, formed by rolling steel while in a semi-molten state.
This manufacturing process gives the RSJ beam strength and durability, making it a crucial element in building and bridge construction.
The RSJ beam’s ‘I’ or ‘H’ shape is designed to efficiently distribute loads, making it well-suited for supporting heavy structures.
I- or H-shaped Advantage of RSJ Beams
1. Strength
The ‘I’ or ‘H’ shape concentrates the material away from the neutral axis of the beam, where it is less effective in resisting bending forces. This results in a stronger beam for a given weight of material.
2. Stiffness
The ‘I’ or ‘H’ shape also provides the beam with greater stiffness. This means that the beam will deflect less when subjected to a load, which is important for preventing structures from sagging or vibrating excessively.
3. Shear strength
The web of the ‘I’ or ‘H’ shape provides the beam with its shear strength. This is the ability of the beam to resist forces that try to push the flanges apart.
4. Stability
The flanges of the ‘I’ or ‘H’ shape prevent the beam from buckling or twisting when subjected to a load. This is important for ensuring the safety and integrity of structures.
Components of an RSJ beam
The main components are as follows:
1. Flanges
The two horizontal members run along the top and bottom of the beam. The flanges provide the beam with its main strength and stiffness.
2. Web
The vertical member that connects the two flanges. The web provides the beam with its shear strength and stability.
Type of steel in RSJ beam
RSJ beams are made from S355 grade steel, which is a hot-rolled structural steel with a minimum yield strength of 355 N/mm².
This grade of steel is strong, durable, and weldable, making it ideal for use in construction applications.
Properties of S355 grade steel:
| Property | Value |
|---|---|
| Minimum yield strength | 355 N/mm² |
| Ultimate tensile strength | 450 N/mm² |
| Elongation at fracture | 24% |
| Reduction in area at fracture | 60% |
| Density | 7.85 g/cm³ |
S355 grade steel is also relatively inexpensive, which makes it a popular choice for RSJ beams. Other grades of steel can be used, but S355 is the most common.
Other types of steel that can be used in RSJ beams include:
- S275: This is a hot rolled structural steel with 275N/mm^2 minimum yield strength. It is suitable for light to medium-duty applications.
- S460: This is a hot rolled structural steel with 460N/mm^2 minimum yield strength. It is suitable for heavy-duty applications.
Common RSJ Beam Sizes and Load Capacities
| RSJ Beam Size | Depth (mm) | Width (mm) | Weight (kg/m) | Maximum Load Capacity (kN) |
|---|---|---|---|---|
| 127×76 | 127 | 76 | 13.0 | 10.2 |
| 152×89 | 152 | 89 | 16.0 | 12.6 |
| 178×102 | 178 | 102 | 19.0 | 15.0 |
| 203×102 | 203 | 102 | 23.0 | 18.0 |
| 254×102 | 254 | 102 | 25.0 | 19.7 |
RSJ beam cost details
Approximate costs for different sizes of RSJ beams:
| Size (mm) | Weight (kg/m) | Approximate cost (£/m) |
|---|---|---|
| 127×76 | 13 | £50 |
| 152×89 | 16 | £55 |
| 178×102 | 19 | £60 |
| 203×102 | 23 | £70 |
| 254×102 | 25 | £80 |
In addition to the cost of the beams themselves, you will also need to factor in the cost of delivery and installation. Delivery costs will typically be around £50-£100 per meter, and installation costs will typically be around £100-£200 per beam.
So, for example, a 3m RSJ beam that is 203mm x 102mm would cost approximately:
- £210 for the beam itself
- £150 for delivery
- £200 for installation
This would give a total cost of £560.
Applications of RSJ Beams
1. Building Construction
These beams are commonly used in building construction, especially in load-bearing structures. Their ability to support substantial vertical loads makes them suitable for creating stable frameworks for buildings of various sizes.
2. Bridge Construction
In bridge construction, where strength and stability are essential, RSJ beams find extensive use. The robustness of steel makes these beams reliable for spanning long distances, ensuring the strength of the bridge structure.
3. Roof Support
Providing support for roofs in various structures, including residential homes and industrial buildings, is another key application of this type of beam. Their strength allows for efficient load distribution, contributing to the overall stability of the building.
Advantages of RSJ Beams
1. Strength and Durability
One of the primary advantages is their exceptional strength. Steel, known for its high tensile strength, makes these beams durable and capable of withstanding substantial loads over extended periods.
2. Versatility
These beams are versatile in their applications. Their adaptability makes them suitable for various construction projects, from residential buildings to large-scale industrial complexes.
3. Easy Installation
Compared to other structural elements, these are relatively easy to install. Their standardized shapes and sizes simplify the construction process, saving time and labor costs.
FAQs
What is an RSJ Beam?
An RSJ (Rolled Steel Joist) beam is a key structural steel component with an ‘I’ or ‘H’ shape, formed through rolling steel in a semi-molten state, offering strength and durability in construction.
Why is S355 Grade Steel Common in RSJ Beams?
RSJ beams are commonly made from S355 grade steel due to its high strength (355 N/mm²), durability, weldability, and cost-effectiveness in construction applications.
What are the common sizes and load capacities of RSJ Beams?
Common RSJ beam sizes include 127×76, 152×89, 178×102, 203×102, and 254×102, each with varying depths, widths, weights, and maximum load capacities.
