KNOWING MS RODS or REBARS

Disclaimer: Information placed here is for basic understanding of the item only. Please consult an engineer / expert for in-depth knowledge.

Mild steel rebar is commonly known as MS Rod.

What to look for before buying rods?

• BSTI Standard. In 2006, BSTI published the standard BDS ISO 6935 for MS rebars.

• Yield strength and Tensile Strength. Yield strength is the maximum stress a material can endure beyond which it begins to permanently deform, not able to return to its original dimensions. Whereas, tensile strength is the maximum tensile stress beyond which a material fails and breaks.

• Grades of Rebar. Grade represents the unit of measurement for stress and tensile strength in materials. Rebar comes in multiple grades, with specific grades depending on the standards within that region. The most five common grades in Bangladesh are 40, 60, 75, 80, and 100. Grade 40 rebar has minimal yield strength of 40,000 pounds. Grade 60 or 60 KSI rebar has minimum yield strength of 60,000 psi. It means that it can withstand a pressure of 60,000 pounds per square inch or approximately 420 MPa. Normally rebars used in common residential building in Bangladesh are of 60 grades (must consult engineer). Heavy structures like bridge need higher grades.

• TMT 500W. TMT means ‘Thermo Mechanically Treated’. ‘W’ means this bar is weldable. A reinforcement bar which possesses yield strength of 500 Mega Pascal (MPa).

• How do you read a rebar code? The first letter or symbol identifies the producing mill. The next marking is the bar size / diameter. The third marking symbol designates the type of reinforcing steel, usually either “S” for carbon-steel or “W” for low-alloy steel. If there’s another number there, that normally show rebar grade.

• How numbers translate into Rebar size? The number represents diameter of rebar, which is divided by 1/8 to denote in inch. That means number #4 rebar is 4 multiply by 1/8″ to denote it 1/2″ (half inch). Similarly #5 bar is 5/8″; #6 bar is 3/4″ and so on.

• Size of commonly used rebars in Bangladesh. The most common sizes for home builders are: 8mm, 10mm, 12mm, 16mm and 20mm. In Bangladesh, often the term ‘Suta’ is used to denote size.

• For seismic resistant design, the yield and ultimate strength and the amount of elongation is very important. The tested yield strength must be equal or greater than the rated strength of the bar but at the same time it shall not exceed the rated strength by 125 MPa. For example, for Grade 420 rebar, the tested yield strength shall be between 420 MPa and 545 MPa (420+125). The ratio of tested ultimate strength and tested yield strength shall be 1.25 or higher.