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Both concrete and metal structures have many applications in the construction industry. But it should be seen what is the difference between concrete and metal structures and comparing these two types of structures, in which fields each is more useful, how are their connections made and what are the advantages and disadvantages of each one compared to the other. including important things such as the use or non-use of bolts and nuts in the connections of these structures. In addition to young engineers in fields such as civil engineering, road and construction, and architecture, knowing these details can be useful even for ordinary citizens. Especially those who want to buy a house or newly built apartment units.

Types of structures:
First of all, we must clarify this issue that, contrary to what many people think, structures are basically of two types:

• Natural structure

• Artificial structure

This category does not need to be introduced, but the second type or artificial structures are divided into several categories, including:

• Concrete Structures

• Metal

In the following, we want to compare these two types of structures. Of course, as you know, what is meant by metal or concrete structure is actually their skeleton, and in fact, if we want to deal with this topic according to scientific principles, we should say the comparison of metal skeleton structure and concrete skeleton structure. Another important issue is the use of bolts and nuts in structures. Today, metal structures can be divided into two categories according to the type of connection:

• Bolted metal structure

• Welded metal structure

Both methods are used in metal structures today. This means that when designing and performing calculations for any type of these structures, for some reason, engineers may consider using bolts and nuts or other methods such as welding to connect different parts of these structures.

In the following, in addition to the general comparison of metal (steel) and concrete structures, we will also compare bolt and nut structures and welded structures.

How to choose the right structure:
Metal and concrete structures each have advantages over the other, and most buildings and skyscrapers use one of these two types of structures. However, the selection of the type of structure in the countries of the world by engineers is subject to various conditions, such as:

• climate

• Existing infrastructure and space

• Height and span of columns

• The type of soil in the area

• Construction cost

• The structure’s resistance to earthquakes

• Stability against fire

• Ease of implementation

• Corrosion rate

• Durability of the structure

• Elastic properties of the structure

Usually, the builders of residential or office, commercial units, according to the mentioned conditions and the above cases, choose the type of skeleton, i.e. concrete or metal. Naturally, in any case, there is a need to take special measures and take into account certain conditions, such as, for example, in order to use and erect metal structures, it is necessary to use bolts and nuts (such as bridges or stadiums) or welding (in tall buildings). ) is the direction of connections.

In the following, we will examine the details as well as the advantages and disadvantages of each of these two types of structures:

Concrete Structures:

Today, concrete structures (in English: concrete frame) are one of the most popular and widely used types of structures in the world, and many famous buildings and structures in the world have concrete frames. Concrete has many advantages in construction, and for this reason, concrete buildings and structures form a major part of structures in today’s world. As you know, in these structures, unlike metal structures, methods such as welding or bolts are not used in connections.

So far, scientists and researchers have written many books and articles about the importance of concrete and its role in building construction, and have investigated the strengths and weaknesses of concrete frame structures. To build a concrete structure, concrete and rebar should be used, for this purpose, the rebar of the columns and beams of the structure is woven first, and then the mold is prepared by pouring concrete. Due to the need for concreting and concrete hardening, the construction of concrete structures usually takes longer than metal structures.

Advantages of concrete structure:
Concrete structures have several advantages, including:

• Lower cost of construction and maintenance

• Greater resistance to moisture (under suitable operating conditions)

• Having high resistance to fire and heat

• Ability to run in different periods

• More homogeneous materials

• Availability and abundance of materials such as reinforced concrete, cement and rebar

• The need for less knowledge and expertise in design

• No need for welding or installation of bolts and nuts

• More suitable connection of columns and diaphragm to the ceiling

• Having proper stability and durability of bending frames

Disadvantages of concrete structure:
• Need to spend more time for concrete reinforcement and molding

• The need for soil laboratories to test concrete

• Increased weight compared to metal structures

• Reducing the strength and stability of the structure over time

• The need for a false ceiling

• More pressure during an earthquake due to the heavier weight of the structure

• Narrowing the space

• More waste of materials

• Possibility of postponement or longer work in case of weather changes such as rain

Metal:

Today, metals or alloys such as steel are used for the construction of many buildings, especially skyscrapers. Metals are scattered all over the planet and mankind has long learned how to use them. Especially in road and construction industries. Because the use of metals is very economical and appropriate due to having a suitable melting point, the ability to conduct electric current, the ability to weld, the use of bolts and nuts or riveting, the ability to be flexible and other things.

Of course, in metal structures, important points should be considered, such as the type of connections (welding the structure or installing bolts and nuts) as well as other things such as the possibility of fire or the presence of