What is a metal box frame and where is it used? This metal frame consists of a network of vertical columns and horizontal beams, which are used in construction. Due to their geometric shape, they have high resistance and can bear the loads of floors, ceilings, and columns. They play an important role in increasing the strength of buildings. In recent years, engineers have designed steel sections to help reduce the weight of structures. In this article, we aim to provide more information about this metal frame; therefore, if you would like to learn more about it, stay with us until the end of the article.
What is a metal box frame?
A metal box frame refers to a completely steel structure made from various profiles, such as I-beams, square tubes, and column tubes. The invention of the first square tube is attributed to James Whitehouse in 1825. In the 19th century, it was used for building truss bridges, and later its use became common in metal structures. The strength of this metal frame largely depends on the size and weight of the profiles used. They are made from steel beams and columns, and the arrangement of the columns can be either vertical or horizontal. One of the main materials used in constructing a metal frame with square tubes is steel sections.
Features such as high strength and resistance, weldability, and good formability of these steel sections have made them suitable for use in metal box frame construction. This reduces the weight of the structure while simultaneously increasing its resistance to impact and pressure. The connection of the metal frame components is done using methods such as welding or bolts and nuts. In the horizontal sections, steel beams are used, which have high resistance to the loads applied to their axes, while the vertical sections consist of metal columns that transfer the applied loads.
Suggested reading: Steel skeleton of a three-story building
Types of metal box frames
Vertical columns and horizontal beams in a metal frame building are connected in various ways. Two methods used for these connections are bolting and welding, which we will introduce separately below.
✅ Bolted Metal Frame
In a bolted metal frame, as the name suggests, all steel columns and beams are connected using bolts and nuts, forming the initial steel structure of the building. This type of metal frame is considered one of the best.
To execute this frame, beams and columns are first produced in a factory or workshop, then transported to the construction site using cargo vehicles, where the columns and beams are connected with bolts and nuts. One of the advantages of this method is the high speed of construction, making it a preferred choice in building projects.
✅ Welded Metal Frame
In this method, all components, including beams and columns, are transported to the construction site and then welded together after being cut to size. To ensure this frame is executed properly, it is essential to involve a skilled specialist with high proficiency in welding.
It’s worth noting that this steel frame method is suitable for small buildings with simple layouts and limited area, as welding and connecting components for larger structures can be very challenging. For a quality welded frame, the quality of the welds is crucial. If the welding quality is poor, the overall strength of the structure may be compromised, leading to significant damages in the future.
How is the Design of the Metal Box Frame Done?
As mentioned, vertical columns and horizontal beams are utilized in the construction of a metal box frame. This arrangement forms rectangular grids. Square tubes can be used in certain parts of steel structures, but their use must comply with building codes and regulations.
The metal box sections used for columns can only be considered for buildings with a maximum of two stories, as there is limited capacity to reinforce the column section at the connection between the beam and the column. For this reason, they are more commonly used in the construction of villas and single-story buildings. If you wish to use square tubes in the frame of multi-story buildings, you will need to fill the inside of the box with concrete to enhance its resistance to earthquakes.
Suggested reading: prefabricated metal skeleton
Stages of Constructing a Metal Box Frame
To construct a metal box frame, the following steps must be followed, just like in other types:
➕ Step 1: Design
The first step involves designing the metal frame with square tubes. For precise design, experienced engineers and engineering software should be consulted. This phase determines which type of box profile and what size should be used based on the applied loads and environmental conditions.
➕ Step 2: Material Procurement
After finalizing the design, the next step is to procure high-quality box profiles from reputable suppliers.
➕ Step 3: Cutting and Preparation
In this stage, the box profiles are cut according to the design, and then they are assembled at the designated location.
➕ Step 4: Connecting the Box
After cutting, the box profiles need to be connected. Bolting or welding methods are used for these connections. While welding is a quick and practical method, using bolts allows for more flexibility, enabling easy disassembly and reconstruction in the future.
➕ Step 5: Quality Control
In the final stage, the metal frame is inspected, and supervising engineers and quality control specialists assess its strength and accuracy.
What are the Advantages of Using Square Tubes in Metal Structures?
While the use of box profiles is common in metal structures, their application in concrete structures presents challenges. The advantages of using these square tubes for steel structures include:
- High strength relative to weight.
- Minimal absorption of external forces.
- Good weldability and formability.
- High resistance to torsion.
- Excellent surface quality.
- Environmentally friendly (does not pollute).
Disadvantages of Using Square Tubes in Metal Structures
Although using these square tubes in metal structures offers many advantages, they are not without drawbacks. Some of these include:
If low-quality square tubes are used, problems can arise in the structure.
- Hollow tubes cannot be used for upper floors.
- Installing connections between the tubes requires a large number of skilled and specialized workers.
- If the surface of the tube experiences corrosion, hydrogen is released, leading to swelling and perforation of the tube.
- Corrosion can change the color of the tube.
- If a metal tube becomes corroded, the structure is compromised, reducing its strength.
- To use square tubes in construction, large, moisture-free storage facilities are needed to keep them.
- Since access to the inside of the column section is not possible, these columns cannot withstand seismic and thermal loads effectively.
- They are not resistant to moisture and corrosion due to the inability to paint the interior.
Suggested reading: metal skeleton of the greenhouse.
Conclusion
With the advancement of science and technology, a new door has opened in the world of industry. Throughout history, various materials have been used to construct buildings. Metal is one of humanity’s significant inventions that has brought about a major transformation in various industries, including construction. To ensure the structural integrity of a building, a strong frame is essential. In this article, we provided information about metal box frames. If you are considering using this type of metal frame for a building you plan to construct soon, you can contact our experts and benefit from their consultation at Saman Dezh.
