different types of metal structures and their features, advantages and disadvantages (part1)
Metal structures is refered to all engineering tools in small and large dimensions. Metal structures or Steel structures entered the industry with the construction of cast iron arched bridges, and many of the world’s most famous structures, such as the Eiffel Tower, the Golden Gate, the Burj Al Khalifa in Dubai, and others, are now built using steel structures. In the following, the types of metal structures are introduced.
What are the types of metal structures?
This type of metal structures is divided into four general categories of framed structures, shell, suspended and truss, depending on the type of bearing forces applied to it. In the following, each category of metal structures is discussed in detail.
Frame or framed metal structures
Framed structure is one of the most common types of metal structures and it can be attributed to all structures whose skeletons are made using shaped steel profiles.
This type of metal structures is widely used for the construction of high-rise structures, towers, residential and industrial buildings, sports structures and sheds. Steel structure is a common type of frame metal structures that can be referred to.
As the name implies, this structure constitutes only the skeleton, frame or frame of the structure, and other parts, such as the roof and walls, can be used from other building materials. Of course, sometimes steel roofs with the brand of steel deck are also used for frame metal structures, which is done according to the budget and design of the structure.
In the frame metal structures, steel profiles are made using steel profiles and columns using the bolt and nut method, which is done in the factory or in the workshop. Of course, sometimes the welding method is used to connect beams and columns, which is obsolete and not approved by the Building Engineering System Organization.
It goes without saying that for the construction of frame metal structures, sometimes steel profiles with square or circular cross-section are used, which are calculated and determined in the design stage of the structure according to the weight of the structure and the forces applied to it.
Advantages of frame metal structure over concrete
The advantages of a frame metal structure over its concrete competitor in low-rise buildings can be mentioned as follows. The frame metal structure has more control over its manufacturing process because it is assembled at the factory and installed on site.
Other advantages of frame structures include more bearing weight and lateral and vertical forces in them than concrete structures.
Disadvantages of frame metal structures compared to concrete
As you know, when iron is exposed to humid air, it rots and rusts, which should be painted with anti-corrosion paints immediately after installing the frame metal structure.
On the other hand, low fire resistance of metal structures should also be considered. As the temperature rises, the iron deforms, causing debris to fall. Fortunately, arrangements have been made for these conditions, the most important of which is the application of fireproof concrete, gypsum or polymer coatings.
Types of frame steel structures
This types of metal structures is divided into two categories: simple frame and flexural frame, which are used to deal with lateral forces on the structure, such as earthquake force. A simple frame system is a system in which all the joints are articulated and it is not possible to exchange anchors.
In this system, the only task of the frame is to transfer dead and live loads to the foundation. On the other hand, the function of the bending frame is to resist lateral forces and they are divided into different types such as ordinary, medium and special bending frames.
Structures whose skeletal structure is made of steel frames include many categories and types, the following are the most important applications as well as the types of their joints.
Structure of steel frame system of industrial sheds and workshops
Silos and workshops are divided into workshops with light and heavy metal frames. The structural system of these workshops consists mainly of steel columns, main beams or rafters, struts, cotyledons (Z), bras and vertical and roof braces and other components.
The main structure of the steel frame of this structure is such that it can be single-span, multi-span and single-story or multi-story, and their economic length is about 24-30 meters.
Bending frame or rigid frame
Rigid frame, continuous frame or flexural frame, is one of the types of systems used to execute steel frame structures. In this system, the ends of the load-bearing members of the structure are connected to each other by rigid connections. Therefore, it is not possible to have a relative rotation of the members of the steel bending frame structure at the joints.
In this way, if a load is applied to the structure, its various components, as a single body, resist deformation and bending anchors.
The metal structure of the bending frame has good strength against vertical and lateral loads. The rigidity of this type of frame structure is provided by the rigidity or flexural stiffness of the set of beams and columns.
The steel structure of the bending frame usually has openings between 12 and 30 meters, screw or welded joints and I-shaped profiles. Based on the expected inelastic deformation, the type of joints used, the quality control level and the use (seismicity of the range) are divided into the following types:
Simple bending frame or OMF
Medium bending frame or IMF
Special bending frame or SMF
The rigid frame system can be used to build steel structures with large open space, high height and long openings.
Cold light steel frame structure or light steel frame structure
Light Steel Frame or LFS system is one of the new construction systems with different uses. During the cold rolling process, thin sheets of galvanized steel are converted into building profiles required for the implementation of load-bearing and non-load-bearing elements of the structure.
Lightweight steel frame profiles are used for residential, commercial and industrial buildings. Low weight and drywall performance improve the dynamic performance of the structure against seismic loads.
High advantages (ability to work as a prefabricated skeleton), good quality of joints and reducing the volume of concreting required for the foundation are other advantages of LSF structure.
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