Now, let us go through some of the quarries related to the rolling margin of steel.
1. What is the rolling margin of steel?
The allowable margin in the percentage deviation of the actual unit weight of a steel bar from its standard or theoretical unit weight is called the rolling margin of steel.
or in other words
The percentage difference in the theoretical and the actual weight of the steel bar per meter length should be within a permissible limit as per IS-1786 (2008). The allowable margin for the steel bars to maintain the sectional diameter, so that the weight of the manufactured steel should be within a specified percentage, in comparison to its standard weight is called the rolling margin of steel.
2. What is the meaning of rolling of steel?
While manufacturing the steel metal, they are passed through the pair of rolls to impart a required dimension and specified properties to the metal. This production process of steel materials is said as rolling of steel.
3. Why it is necessary to calculate the rolling margin of steel?
When we procure the steel bars for the construction work, the weight of the bars received on-site, always differs from the theoretical weight.
The standard weight of the steel bar is calculated, based on the theoretical density & diameter of the specified bar. But in the practical world, it is difficult to maintain the exact bar diameter & density, during the manufacturing process of the steel bars.
The bars so produced may be underweight, standard weight, or maybe overweight.
Since the procurement of construction steel is always based on weight, the length of the overweight bars will differ from the theoretical length, and ultimately we will fall short of the required bar length.
This bar shortage cumulatively affects the calculated project cost, making us spend more to procure the extra steel bars to complete the construction project.
Similarly, if the purchased steel bars fall in the underweight category, that will affect the design strength & stability of the building. The sectional percentage of underweight steel bars used in the construction project will be lesser than the designed requirement, which may break the safety standards.
So, in order to curb such mistakes, it becomes necessary to calculate the rolling margin of steel.
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4. What is the allowable rolling margin of steel as per IS code?
IS-1786 (2008 ) has set a standard to calculate the rolling margin of steel in percentage, to maintain the safety of buildings, to complete the construction work in a given time, & to limit the loss in the calculated project cost.
Allowable deviation in weight of the reinforcement bars of different diameters as per IS- 1786 are as follows.
8mm to 10mm 👉 ±7%
12mm to 16mm 👉 ± 5%
20mm and above 👉 ± 3%
Thank you for going through this article❤. Have a good day 😄.
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