Metallic skeleton is suitable for tall structures; however, a limited number of floors can be constructed with a concrete skeleton.
The durability and high strength of steel allow for prolonged use of a metal skeleton, a condition not explicitly met by a concrete skeleton.
The execution of a steel structure or metal skeleton is easy and can be done at a high speed. The need for time to set concrete and execute the next phase demands a considerable amount of time for the construction of a concrete skeleton.
The weight of a structure built with a metal skeleton is significantly less compared to a structure built with a concrete skeleton, which is one of its advantages and, overall, contributes to reducing the building’s weight.
Steel is a homogeneous material and is manufactured under precise supervision in a factory, while concrete is produced in a workshop, and its homogeneity is not as consistent as steel.
Since steel possesses elastic properties compared to concrete, steel structures or structures with a metal skeleton have high resistance against large compressive forces such as explosions and lateral forces like earthquakes.
Stages of implementing a two-story metal skeleton building
Below, information is provided on the implementation process and stages of a metal skeleton in multi-story buildings, inviting your attention to it.
Excavation
Excavation is a stage that must be carried out in both steel and concrete structures. Generally, excavation is done until reaching the virgin soil, and for structures with a basement, more extensive excavation is performed.
Concrete Pouring (Moghr)
After excavation and soil testing, the next step is concrete pouring (Moghr). This concrete pouring is done to protect the pile foundation and create a smooth surface for the construction process to continue.
Moghr concrete, as mentioned, should provide a smooth surface for the continuation of work; therefore, it contains a lower amount of cement to flow easily and cover surfaces smoothly, ultimately providing a smooth surface.
Reinforcement
After the Moghr concrete is executed and maintained, the next step is reinforcement, which is essential for both concrete and steel structures.
After reinforcement, the installation of column plates and formwork is done. This stage does not differ significantly between the two types of structures. It should be noted that the reinforcement must comply with the standard principles of national building regulations.
Concrete Pouring (Pile Concrete)
After reinforcement and formwork, the process of concrete pouring begins. This stage of concrete pouring is carried out for pile execution. The concrete used can be prepared in the workshop or purchased from concrete manufacturing companies. In any case, before pouring concrete, the mixer must thoroughly mix the concrete to ensure its homogeneity.
In this stage, concrete should be poured onto the reinforcement from a close distance, and after each pouring stage, vibration should be used to mix and homogenize the concrete. To prevent concrete corrosion and create cracks, its surface should be kept moist, which is referred to as the maintenance stage. After the initial setting of concrete, the forms are removed, and the maintenance and moistening process continues.
Slab Forming
Slab forming is a process in which steel plates supporting the beams are securely attached to specific reinforcements. Part of the slab forming operation, known as “hoagiri,” is performed when the concrete has not fully dried.
In the hoagiri stage, a significant amount of loose concrete is poured under the steel plates, and then the plates are pressed into place with screws to eliminate any voids underneath.
It is worth remembering that the presence of empty spaces under the plates can lead to settlement in the columns when the columns are executed, especially with an increase in weight. Therefore, loose concrete is used underneath them for hoagiri.
Column Execution
For column execution, iron beams are ordered from the factory. The height of the column is measured, and the required amount of iron beams is brought in. Iron beams with fewer counts are then welded to the iron beams of the first floor using metal plates to execute the second-floor skeleton. This is done to reduce the dead load of the building and decrease the thickness of the columns.
When the beams are ready, they are lifted vertically using a crane and firmly placed in their designated locations, which are the metal plates prepared in the reinforcement and slab forming stages. The connection of the column to the plate is usually done by welding or screwing. It should be noted that corners are pre-screwed onto the plates for better connection to the column.
Beam Execution
Beams are tall metal pieces that connect columns and, in continuation, the process of beam detailing, floor or ceiling execution is carried out. The iron used for beams is different from the iron used for columns.
To execute the beams, they first bring the beams to create greater resistance in a beehive-like pattern. In this stage, using a gas-cutting machine and a template, hexagonal cuts are made on the body of the iron beams at specified intervals to increase the beam’s resistance. Then, the remaining hexagonal plates are used to connect the beams to the columns.
Wind Brace Execution
It can be said that the last stage of the metal skeleton execution is the execution of wind braces. Usually, pairs and single struts are used for wind brace execution, connected in a cross shape from the connection point of one column and beam to the connection point of the next column and beam.
Finally, at the intersection of the wind braces, metal plates are used to increase the skeleton’s resistance against lateral forces. It should be noted that the execution of wind braces involves fine details and specific execution points not covered in this section.
Final Words
In conclusion, after the execution of wind braces and the installation of stairs between the floors, the execution of the two-story metal skeleton building comes to an end. Subsequently, the process continues with beam detailing and the execution of the ceiling and walls, followed by the commencement of the finishing work.
