What Is Rolled Steel Joist (RSJ) Beam? RSJ Vs Universal Steel Beam

What Is Rolled Steel Joist (RSJ) Beam?

A rolled steel joist (RSJ) is a common type of beam used for structural steelwork. It is also known as an ‘I-beam’ or ‘H-beam’ and comes in a variety of standard sizes.

RSJs are usually made from mild steel but can also be formed from aluminium or other materials. They are formed by hot rolling, cold rolling, or by extrusion.

RSJs are used in construction and civil engineering for supporting structures above openings. The height, width, and weight (in kg per metre) of the RSJ must be taken into account when calculating the load it will bear.

Installing an RSJ correctly requires careful calculations, time, and skill by an experienced builder or structural engineer. The cost of installing an RSJ can vary greatly depending on regional price differences between suppliers, the size of the beam, and the ease of access to your property.

What Are RSJ Beam Sizes?

General guidance to know the best RSJ size for a 3m span is 152x89x16, in which the depth of the RSJ beam is 152mm, the width of the flange is 89mm and 16 is the weight in kg per metre. The depth of a beam can be roughly estimated by dividing the span length by 18 to 20 mm.

Universal Beams (UBs) or I-Beams are steel sections available in a range of sizes, weights and finishes. The parallel flange of the Universal Beam does away with the need for tapered washers and makes it easier to connect than Rolled Steel Joists (RSJs).

The cross-sections are commonly specified with a code consisting of three dimensions: depth, width and weight in kilograms per metre.

What Is The Minimum Bearing For RSJ?

The minimum bearing for an RSJ (Rolled Steel Joist) is 100mm. If the RSJ is offset, then an allowance should be made in the overall length.

The anodized aluminium alloy carriage plate can be manufactured to the customer’s special length requirements, but the bearing assembly mounting hole centres must have a minimum of 150mm (6 inches).

Depending on the length of the steel, it is recommended to have a 200mm bearing on each end. The holes for bearing assemblies should be reamed to tolerance as per dimension ‘R’ on page 17.

What Is The Purpose Of A Steel Joist?

The purpose of a steel joist is to provide support for floors and roofs. Steel joists are open-web, secondary load-carrying members that are 144 feet (43.9 m) or less in length and designed by the manufacturer.

They are made from an alloy that includes at least 50 percent iron, between .02 and 2 percent carbon, and may include other elements.

Steel joists can be used to support concentrated loads in-plane, and must be set in tandem with all bridging installed when spanning more than 60 feet (18.3 m). Connections of individual steel joists to steel structures in bays of 40 feet (12.2 m) or more must also be field-bolted.

What Is Maximum Load-Bearing Capacity?

The bearing capacity of a foundation is the maximum load that can be applied on a foundation before failure or uncontrolled deformations occur.

The allowable bearing capacity (qa) is the maximum bearing stress that can be applied to the foundation such that it is safe against instability due to shear failure and the maximum tolerable settlement.

The ultimate bearing capacity (qf) is the value of bearing stress which causes a sudden catastrophic settlement of the foundation (due to shear failure).

The ultimate load capacity of a footing can be estimated by assuming a failure mechanism and then applying the laws of statics to that mechanism.

The maximum safe bearing capacity is the maximum value of contact pressure to which the soil can be subjected without risk of shear failure.

The allowable bearing pressure is according to AS2870-1996 (Residential slabs and footings-Construction) the maximum bearing pressure that can be sustained by the foundation from the structure’s weight.

The exact load-bearing capacity will depend on factors such as soil type, footing shape, and overburden pressure. It should also be noted that there are different methods for calculating load-bearing capacities, such as finite element methods or zone load tests.

Difference Between an RSJ and a Universal Steel Beam

An RSJ (Rolled Steel Joist) and a Universal Steel Beam are both types of structural steel beams commonly used in construction. They have some similarities but also key differences. Here are the primary distinctions:

1. Cross-Sectional Shape:
   • RSJ (Rolled Steel Joist): RSJs typically have a more “I” or “H” shape when viewed in cross-section. The vertical section is known as the web, and the horizontal sections at the top and bottom are called flanges. RSJs are designed to efficiently support loads in both bending and shear.
   • Universal Steel Beam: The term “Universal Beam” is more common in British and European construction, and it often refers to what is known as an I-beam in other regions. It has a similar “I” shape with a vertical web and horizontal flanges.
2. Manufacturing Process:
   • RSJ: The term RSJ often implies that the beam has been rolled into shape. The rolling process involves passing a piece of steel through a series of rollers to achieve the desired shape.
   • Universal Steel Beam: This term is more generic and can refer to various types of steel beams. Universal beams can also be produced through the rolling process.
3. Standards and Nomenclature:
   • RSJ: The term RSJ is more commonly used in the United Kingdom and is associated with British and European standards.
   • Universal Steel Beam: This term is also used in the UK and Europe but may refer to a broader category of steel beams.
4. Sizes and Dimensions:
   • Both RSJs and Universal Steel Beams come in various sizes and dimensions to accommodate different structural requirements. The choice of beam size depends on factors such as the span of the structure, load-bearing capacity needed, and engineering specifications.

Differences between an RSJ (Rolled Steel Joist) and a Universal Steel Beam: