The following advantages in general may be credited to steel as a structural design material:
Steel has a high strength/weight ratio. Thus, the dead weight of steel structures is relatively small. This property makes steel a very attractive structural material for
a. High-rise buildings
b. Long-span bridges
c. Structures located on soft ground
d. Structures located in highly seismic areas where forces acting on the structure due to an earthquake are in general proportional to the weight of the structure.
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As discussed in the previous section, steel can undergo large plastic deformation before failure, thus providing a large reserve strength. This property is referred to as ductility. Properly designed steel structures can have high ductility, which is an important characteristic for resisting shock loading such as blasts or earthquakes. A ductile structure has energy-absorbing capacity and will not incur sudden failure. It usually shows large visible deflections before failure or collapse.
Predictable material properties
Properties of steel can be predicted with a high degree of certainty. Steel in fact shows elastic behavior up to a relatively high and usually well-defined stress level. Also, in contrast to reinforced concrete, steel properties do not change considerably with time.
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Speed of erection: Steel structures can be erected quite rapidly. This normally results in quicker economic payoff.
Quality of construction: Steel structures can be built with high-quality workmanship and narrow tolerances.
Ease of repair: Steel structures in general can be repaired quickly and easily.
Adaptation of prefabrication: Steel is highly suitable for prefabrication and mass production.
Repetitive use: Steel can be reused after a structure is disassembled.
Expanding existing structures: Steel buildings can be easily expanded by adding new bays or wings. Steel bridges may be widened.
Fatigue strength: Steel structures have relatively good fatigue strength.
Disadvantages of Steel
The following may be considered as disadvantages of steel in certain cases:
General cost: Steel structures may be more costly than other types of structures, and other materials are cheap from steel. therefore more cost of steel is disadvantages of steel.
Fireproofing: The strength of steel is reduced substantially when heated at temperatures commonly observed in building fire. Also, steel conducts and transmits heat from a burning portion of the building quite fast.
Consequently: steel frames in buildings must have adequate fireproofing.
Maintenance: Steel structures exposed to air and water, such as bridges, are susceptible to corrosion and should be painted regularly. Application of weathering and corrosion-resistant steels may eliminate this problem.
Susceptibility to buckling: Due to high strength/weight ratio, steel compression members are in general more slender and consequently more susceptible to buckling than, say, reinforced concrete compression members. As a result, considerable materials may have to be used just to improve the buckling resistance of slender steel compression members.
written by : Engr Sami Ullah Stanikzai
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