Steel Structures
Steel Structures and their Uses
Since construction is ordered until installation, no other construction system is comparable with prefabricated steel structures system considering being economically economical, flexibility, high construction speed and easy installation and also as steel is produced in factory and considering better conditions of steel quality control rather than concrete, steel and metal structures, it is different from concrete and other construction materials
Among the Advantages of Metal Structure Are:
* It is possible to develop structure after finishing
* It is possible to connect some pieces to each other
* There are some prefabricated pieces in factory
* Operating and installing them have high speed
* It occupies less space than concrete
* And it is used in high height
In experts’ point of view using prefabricated steel structures in fast constructions as well as the quality of commercial, medical, industrial and residential infrastructures are among the reasons that why newfound countries have developed rapidly.
Steel Structures Advantages:
1. Steel High Resistance
As metal pieces have high resistance and they are more resistant against weight rather than bigger concrete materials, these are important in big openings of sheds and high buildings, especially buildings which are on loose ground.
2. Steel Consistent Properties
Metal is produced in big factories under accurate supervision and its consistent properties are ensured and its properties are not influenced by external factors despite unlike concrete. Ensuring materials properties is effective in selecting smaller factor of safety which causes materials economization.
3. Steel Durability
Steel is durable enough, it is operational for long time if metal is preserved structurally well.
4. Steel Elastic Properties
Steel elastic properties have practical instances with very good approximation, steel follows Hook’s Law in big stresses.
5. Steel Ductility
Ductility is one of metals positive properties which may prevent stress concentration which is in fact the reason of damage and tolerates dynamic force and impulse, while concrete materials are highly weak against these forces as they are very crispy and fragile. This prevents steel structures damage suddenly and there is enough time to evacuate people and repairs.
6. Steel Pieces Continuity
Since metal pieces are made up of homogenous and continuous materials, they show better continuity form themselves during earthquake, but damages are exerted to concrete film on rebar in concrete pieces during every earthquake and some cracks happen in concrete film which are not controllable and probably building will be weaker and damaged more in next earthquake and aftershock.
7. Steel Materials Balanced Resistance
Metal materials are the same in traction and pressure and they are almost as resistant as traction and pressure, therefore, loads are changed without damage that is nothing will happen when transforming compressive power to traction. Concrete has good resistance in pressure but it is low in traction and or shear in reinforced concrete buildings, so regions which are probably influenced by tractive force or they have not been reinforced well, they produce crack or damage.
8. Explosion
Steel structures have better behavior against explosion rather than concrete buildings.
9. Easy Construction and Installation
Preparing metal pieces in factories and installing them in different atmospheric conditions with necessary practicable preparations.
10. Occupy Space
Metal building beams are smaller than concrete building beams in two buildings with same columns in height and dimensions. Gross Floor Area (GFA) is happened more in concrete buildings rather than in metal ones.
11. Installation Speed
Operating and installing metal pieces is significantly higher than concrete ones. It makes finishing work rapidly, on time using from project and spent costs rapid return possible.
12. Improvability and Reinforcement
Weak pieces of metal buildings which are made as a result of computational mistake can be reinforced by welding, riveting and screwing new pieces and adding a part or openings.
13. Losing Materials
Since metal structure pieces are produced in factories, wasted or discarded materials are prepared and applied less that concrete.
14. Steel Buildings Low Weight
The average weight of steel buildings is estimated between 245 to 390 kg/m2 and or 80 to 128 kg/m3, while it is between 480 to 780 kg/m2 or 160 to 250 kg/m3 in reinforced concrete buildings.
15. Increasing Structure Frame Quality
Increasing structure frame quality leads to constructing metal prefabricated pieces with high quality due to controls before, during and after operating structures and also controlling materials perfectly and resident quality control system in construction set considering dimensions and welding.
16. Seismic Power Coefficient
Ground movement as a result of earthquake causes internal forces influence building components. In other words, a building which is on randomly and heterogeneously vibrating ground has to be static and tolerate ground vibration. Reinforced concrete frames weigh more weight have more seismic power coefficient than metal frames, experience shows that loses are more on short an rigid buildings which are built on solid ground also tall and flexible buildings which are built on soft ground are damaged a lot by earthquakes. In other words, constructing short buildings on soft ground with relatively big earth vibration period shows better results. And reversely, constructing tall buildings on solid grounds with small period will have less damage. Buildings reaction against earthquake movement depends on the characteristics of building itself considering rigidity and or flexibility, building vibration natural period is the most important characteristic of building in behaving against earthquake.
17. Materials Full Reversibility
Materials full reversibility of metal structures makes it possible to reuse them especially in bolt and structures.