1.2 ADVANTAGES AND DISADVANTAGES OF STEEL AS A STRUCTURAL DESIGN
The following advantages in general may be credited to steel as a
structural design material:
1. High strength/weight ratio. 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
2. Ductility. 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
3. 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
4. Speed of erection. Steel structures can be erected quite rapidly. This
normally results in quicker economic payoff.
5. Quality of construction. Steel structures can be built with high-quality
workmanship and narrow tolerances.
6. Ease of repair. Steel structures in general can be repaired quickly and
7. Adaptation of prefabrication. Steel is highly suitable for
prefabrication and mass production.
8. Repetitive use. Steel can be reused after a structure is disassembled.
9. Expanding existing structures. Steel buildings can be easily expanded by
adding new bays or wings. Steel bridges may be widened.
10. Fatigue strength. Steel structures have relatively good fatigue
The following may be considered as disadvantages of steel in certain
1. General cost. Steel structures may be more costly than other types of
2. Fireproofing. The strength of steel is reduced substantially when heated
at temperatures commonly observed in building fires. Also, steel conducts
and transmits heat from a burning portion of the building quite fast.
Consequently, steel frames in buildings must have adequate fireproofing.
3. 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.
4. 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.