Welding metal structures
In order to implement a building of welded metal structures, the first step must be to make the building land with sufficient strength to withstand the gravity of the building and not subsidence. For this purpose, firstly, the Earth’s compressive strength test is being carried out by the engineers. To do this, they buckle and sampled from the soil of different classes of land and sent samples to the lab to test and determine the amount of tolerable load. After the lab attempts to determine (which unit is kg / cm2), the structural engineer calculates the footing build-up according to the compressive strength of the soil. Whatever this smaller number, footing dimensions should be larger, and the larger the number, the dimensions of the footing will be smaller. (This number is close to one, which is usually kg / cm2)
Welded joints in steel structures and welded metal structures
Welding metal structures in Iran and around the world are widely used for construction of building, bridge, factory, warehouse and other urban and industrial facilities. Welding is the most common method of connecting metals widely used in the manufacture of metal structures. The quality and strength of the structures depend on the design and then the correct execution of their joints, and if the precautions are not applied, the structure will be severely damaged. Because a metal structure is nothing but a series of steel sections that are connected to each other and stretched, and these joints should withstand tremendous pressure.
Since our region is located in an earthquake zone and the building’s resistance to earthquake-induced forces is critical, the sensitivity of the subject is doubled. Hence, the quality of welding of metal structures should not be overlooked and negligent. In the event of
destruction of structures, there is a lot of damage to the country which in any case is
irreparable.
Advantages of bone connection of welding metal structures
Bone connections in steel flexural bearing frames are reviewed to enhance the existing rigid joints and reduce the bugs of rigid joints in the design of new steel structures. The advantages of this kind of connection are to maintain the compression of the beam cross section and to achieve no significant reduction in hardness and torsion, as well as the reduction of local buckling. A new benchmark was also used to describe the reduction rate of resistance after reaching the maximum load bearing capacity of the sample load.
One of the most important situations in which a structure is damaged by earthquake loads is failure in structural joints. The failure of the joints causes the collapse of the structure and progressive failures. One of the proposed strategies to improve the performance of these types of joints is the application of localized reductions in the beam section known as bone connection. In this case, a slight distance from the column in the form of a topical part of the beam web is cut to reduce the bending capacity of the beam in that area. By doing this, the plastic hinge is created far from the connection of the beam to the column and in the beam itself, and it prevents failure in the connection and welding of the beam to the column.
Bone connection has high ductility and plastic rotational ability and, and by creating a plastic hinge in a narrowed area, while protecting the connection, brings more energy dissipation. Other advantages of bone connection are economic and ease of its execution, so that to make this type of connection, it can be cut into a beam at the factory, and then transferred the beam to the workshop.
One of the problems with bone connection is the reduction of ability to bearing the load due to large displacements. The reason for this is the weakening of the beam wing section and its effect on reducing the cross-sectional resistance to out-of-page deformations, which results in the beam being narrowed to the local and lateral buckling.
The general stages of welding inspection in steel structures are as follows:
- WPS compliance prepared by the project executor with the desired standard
- Welding instruction validation tests (PQR)
- Evaluation of welder and issuance of qualification card
- Testing and controlling all equipments related to welding operation
- Testing and controlling electrode and welding consuming materials
- Inspection and control of preparation of parts
- Control metal temperature degree and preheat operation
- Control precisely welding sequence to prevent complexity
- Numbering of parts and preparation of daily reports of welding operations
- Visual inspection of 100 percent of welds
- Execute other non-destructive tests with a specified percentage
- Monitor the repair of all defective welds
- Documentation and preparation of technical inspection reports
- Certification of welding quality of steel structures
