What is a steel skeleton?
The metal frame consists of steel, beams and columns. The columns of the structure are placed both vertically and horizontally. The most important material used in the metal frame is steel, which is currently one of the most important materials in the construction industry. One of the most important features and advantages of steel, which has led to its use in metal frameworks, is its high resistance, weldability, formability, flexibility, homogeneity and elasticity.
Using this structure in structures and buildings has made them use less weight and show more resistance and strength against any impact, pressure and external factors such as earthquakes. So it can be said that structures with metal skeletons have more relative balance.
✔️ Benefits of metal buildings
High resistance
The strength of steel is high and its strength-to-weight ratio is greater than concrete. This issue is more important in sheds with large openings and high-rise buildings and buildings that are built on loose ground. Balanced strength of materials: The strength of steel is the same in tension and compression, and good in shear and close to tension and compression. In changing the position of the loads, the compressive and tensile force can be replaced and the sections react well. But the strength of concrete is good in pressure and low in tension or shear. So, if areas are subjected to tensile force and are not armed, they will be destroyed.
✔️ Elastic properties
due to the homogeneity of steel Its computational elastic properties have a practical example with a very good approximation. Steel follows Hooke's law well up to a wide range of stresses. For example, the moment of inertia of a steel section can be safely included in the calculations. However, in the case of concrete, these figures are not very specific and reliable.
✔️ Seismic force coefficient
In reinforced concrete forms, due to their greater weight, the seismic force coefficient is greater than that of metal frames.
✔️ Characterism
One of the important properties of metal materials is their malleability. Metals are able to withstand stress concentration, which is actually the cause of failure, and dynamic and impact forces, while concrete is brittle and brittle and its performance against these forces is very weak.
✔️ Uniform properties
Steel is prepared inside the factory under strict supervision, so its properties are uniform unlike concrete. Confidence in the uniformity of the properties of the materials causes the selection of a smaller confidence factor, which in turn leads to savings in the consumption of materials.
✔️ Durability
The durability of steel is very good. If sufficient care is taken in the maintenance of metal buildings, they will be usable for many years.
✔️ Connectors of materials
Metal parts are generally continuous and homogenous due to their constituent materials, but in concrete parts, the concrete coating on the rebar is damaged in every earthquake. becomes The cracks that appear in the concrete coating cause the weakness of the piece and there is a possibility that the building will be destroyed in the aftershock or the next earthquake.
✔️ Low weight
The average weight of steel skeleton between 250 to 390 kg/m2 or 80 to 130 kg/m3, while in reinforced concrete buildings these figures are between 480 to 780 kg/m2 or 160 to 250 kg/m3 respectively.
✔️ Occupation of space
in two similar buildings from In terms of height and dimensions, the columns and beams of metal buildings are smaller than concrete buildings in terms of dimensions, which means that the level of occupation of the skeleton or dead space is higher in concrete buildings.
✔️ Steps to make steel skeletons
Each metal skeleton is made up of different parts, for its installation, training should be done both theoretically and practically. . Usually, the technical and professional organization in this field organizes skill courses in every province of the country at some times of the year. In this article, we will briefly explain the important things in each field for your familiarity. The general principles of metal frame installation are given based on written standards and engineering regulations for the construction of various structures, which you can also use from these references.
✔️ Installation of column plate bolts in steel skeletons
The first and most important step to raise a building is the installation of a metal frame, and the first parts of this frame include the bolts of the column plate, which must be installed precisely in their place, that is, the axis of the column plate. In order to install these plates with high accuracy and not need to move them again, mapping cameras should be used to locate them. On the other hand, the bolts should be placed in such a way that they do not move when concrete is poured on them. This work is easily done by using a special template for the column plate and four fixing bolts. This template is a plate with the same dimensions as the column plate, which is made of wood or metal, and is used to fix the bolts and install the main column plate accurately.
Another method is to install the main column plate accurately on the foundation, in this method a tool like a crane is needed and therefore it will take time. On the other hand, there are more implementation problems in this method, and if you are not very careful in its implementation, you may have problems installing the beams later. The last thing you should keep in mind when installing the bolts is that the threaded parts of each bolt should be completely greased and covered with a sack or nylon before concreting. This work makes it easy to open and close the beads of the column plate after concreting.
✔️ Construction and installation of columns in the steel skeleton installation path
When we hear the name of the column, words like resistance, support and stability come to our mind. Because the pillars are always a symbol of the strength and standing of anything. Therefore, in the next step of installing the metal frame, you must learn how to install the columns correctly so that we have a stable building in terms of engineering. The main task of the columns in any structure is to transfer loads to the foundation, so they must be installed in such a way that they fulfill this role well. The best types of sections for columns are square and H-shaped in terms of engineering. These sections have higher resistance than other shapes, and both single and composite sections are used to drive the columns. The composite type is usually used to withstand more compressive forces and bending anchors applied to the column, so which column to use depends on the total load of the structure.
✔️ Construction and installation of beams to complete the installation of steel skeletons
After the columns, we go to the construction and installation of the beams. The construction and installation of beams directly depends on the type of connection, including welding, screwing or riveting, as well as whether the connections are strong or simple. When installing beams, you should pay full attention to points such as welding length, beam length, compliance with beam tolerances, welding type, welding dimension, type of screws required, electrode required for welding, etc. For the construction and installation of beams, one of the four sliding, splicing, hinged and flanged methods is usually chosen depending on the project conditions and the opinion of the employer or contractor. The simplest method among these four is the sliding method, which is more useful in installing the metal frame.
