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Steel is a variety of iron, containing 0.1 to 1.5% carbon in the form of cementite.
It is the most used element in civil engineering construction work. After knowing the unit weight of steel, we can determine the total weight of steel bars required for the project construction.
2. Types of Steel Bars Used in Construction
There are 6 types of steel bars which are described below:
|S.No.||Types of Reinforcement||Sub-type||Relevant Indian standard|
|1||Mild steel plain bar||Cold worked mild steel bars Hot rolled mild steel bars||IS 432-1996 (part –I) Is 1139-1966 (part II)|
|2||High yield strength deformed bar ( Tor steel)||Cold worked deformed bars Grade Fe 415Grade 500Hot rolled deformed bars||IS 1786 – 1979 IS 1139 – 1996 (part – II)|
|3||Hard-drawn steel wire fabric||Wire mesh||IS 1566 – 1967|
|4||Rolled steel members||Angles, T- sections joists, channels, etc.||IS 226 – 1975|
|5||Thermo-mechanically treated bars (TMT)Corrosion resistant steel (CRS) bars||Latest in-use deformed bars|
a. Mild Steel Reinforcement
Generally, the mild steel bars also are termed Fe 250 due to the yield strength of this steel being 250 N/mm2.
Mild steel bars are ductile in nature, they are not recommended over high-yield strength deformed bars because of less strength and weak bond.
The modulus of elasticity of mild steel is taken as 2 x 105 N/mm2. In columns, they are utilized as lateral ties and at places where nominal reinforcement is needed.
b. High Yield Deformed Bars
High-yield deformed bars are also termed HYSD bars. It contains a higher percentage of carbon in contrast to mild steel. High-yield deformed bars’ strength is higher as compared to mild steel, but the yield point is not defined clearly.
The two types of bars are as follows:
a. Hot-rolled high-yield strength bars
b. Cold-worked high-yield strength bars
The (b) form of steel is also termed CTD bars or Tor steel and is found in two grades.
1. Fe 415 or Tor 40
2. Fe 500 or Tor 50
c. TMT ( Thermomechanically Treated ) Steel Bars
Among the components of RCC, steel is that expensive, so the main aim has been more on steel to make it the best and best.
TMT steel contains more strength but has similar features as HYSD. Majorly these types of steel bars are utilized in the construction of various structures.
These bars are prepared by transporting hot rolled steel bars through icy water. The external surface of the bar results to be harder while the internal core is still softer, by this process.
d. CRS (Corrosion Resistant Steel) Bars
The advanced development in steel bars in the manufacture of CRS or corrosion-resistant steel bars. The quantity of carbon added in the CRS bars is 0.18% in contrast to 0.2 % of HYSD bars. A high percentage of corrosion-resisting elements is added which is chromium as high as 1.5%.
e. Steel Wire Fabric
Wire fabric is prepared by welding or weaving steel wire in the configuration of a mesh which is also termed steel wire mesh. This mesh is utilized as reinforcement in slabs, pavements, roads, shells, etc.
f. Structural Steel
For very heavily loaded structures such as foundations & columns rolled sections like rolled steel joists, angles, or channels are fixed in concrete & utilized as reinforcement.
3. Characteristic Strength of Steel Bars Used in Construction
The characteristic strength of steel bars is similar to the minimum yield stress, according to IS 456:2000.
The table provides the values of characteristic strength for different grades of steel and their minimum % change in length.
Characteristic strength and minimum percentage elongation for various steel bars.
|Types of steel||Grade||Yield stress/0.2% proof stress or characteristic strength (N/mm2)||% Elongation ( minimum)|
|Mild steel||Fe 250||250||23%|
|High-strength deformed steel (HYSD)||Fe 415 ( Tor 40) Fe 500 ( Tor 50) Fe 550 (Tor 55)||415 500 550||14.5% 12% 8%|
|TMT or CRS bars||Fe 500||500||12%|
|Steel wire fabric||–||480||7.5 over a gauge length of 8 diameter|
4. Uses of Steel Bar
The uses of steel bars are as follows:
1. Steel Bars are generally used to prepare columns and beams.
2. It is used in bridges, buildings, culverts, etc.
3. It is used in those structures where the structure needs to bear a load.
|Read Also: DPC Treatment in Buildings|
5. Advantages of Steel Bars
The advantages of steel bars are as follows:
1. It provides ductility to the structure.
2. It helps the structure to bear heavy loads.
3. It increases strength and durability.
6. Disadvantages of Steel Bars
The disadvantages of steel bars are as follows:
a. Steel is costly to buy.
b. It is not suitable for hot places.
c. There is a chance of rusting.
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