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Generalization of Rebar

Generalization of Rebar

A rebar or armature is a steel that is used in the concrete to hold its low tensile strength.

Rebar

Rebar armature (in Afghan Persian: sikh-gl), is a steel that is used in the concrete to hold its low tensile strength. A steel that is used for this purpose in reinforced concrete structures is in form of wire or rebar and it is called as rebar steel. However in certain cases, the structural steel such as I-shaped profiles, runner or can also is used to reinforce the concrete. The steel rebars must be clean and free of paint shells, oil, dust and any other contamination, because these contaminations make the adhesions between the concrete and armature reduced. Using of rusty and scaling rebars is not allowed; unless they are thoroughly cleaned by brushing or sandblasting. In this case, if the cross section of armature has weakened, the real weakened cross section should be used in calculations. The section of typical simple armature should be circular and steady and should not weaken at no point by factors such as corrosion and its mechanical features should be in accordance with the provisions of concrete regulation in Iran.

Stirrup

The transverse armatures that are tied around the main longitudinal armatures in quoins to resist against cutting and twisting are called as stirrup.

Rebar binding is used in order to strengthen the building, bridge, dam, etc, a bar bender connects the rebars to each other by tying rebars to each other with a wire.

The rebar’s important computational features

Yield strength

The amount of stress that the steel sample length changing increases in that without increasing the amount of tension is called as Yield Stress or Yield strength and it is displayed with f y.

The rebar spacer

The rebar spacer is an element that is used to create a distance between the rebar and the outer surface of the concrete.

Tensile strength

It is achieved by dividing the maximum recorded load in tension test by the primary section level.

The steel rebar classification

The rebar steel is produced with different standards in different countries and there is a specified classification in each standard in related to the mechanical properties of steels. The majority of rebar steels in Iran that are produced by Esfahan Steel Company conform to Russian standard. The steel that is produced in Iran (according to Russian standard) divides to three groups: A-1 steel, A-2 steel and A-3 steel.

A-1 steel is in flat steels and its Yield strength and Tensile strength is 2400 and 3600 kilograms per square centimeter. A-2 steel is in ribbed steels with 3400 kilogram per square centimeter Yield strength and 5000 kg per square centimeter Tensile strength, and A-3 steel is also in ribbed steels with 4000 kilogram per square centimeter Yield strength and 6000 kilogram per square centimeter Tensile strength.

In terms of rebars diameter variety, the manufacturers’ standards are different. In Russian system that is used in the Esfahan Steel Companies, the rebars are manufactured up to 40 mm in diameter.

The only permissible and applicable method to weld rebars to each other is the head to head in rebar forge welding that is done by using of pressuring while heating by Oxygen gas and Acetylene.

History of using of rebar in the concrete

The steel consumption in the concrete became common after an evolution and development as follows:

1-The first reinforced concrete has been armed with building a concrete shovel for a boat by square nets in rectangular shape, iron bars, was established by lambot in 1848.

2-one reinforced concrete water resource was built with a 120 square meters capacity by moneer in 1873.

3-((steel concrete theory)) (in the book ((moneer system)) was set up based on three principles by ((ways)) and ((konen)) in 1887 as follows:

  1. In a member of reinforced concrete, all the tensile forces are tolerated by steel.
  2. Based on joint action principle, power transmission to steel is done by the adhesion of concrete and steel.
  3. The volume changes of concrete and steel is approximately equal by effect of temperature changing.

4-A comprehensive characteristics about concrete and reinforced concrete physical and chemical properties were determined by American Society of the International Association for Testing and Materials in 1936.

5-The reinforced concrete structure was evolved by pursuits and studies in different countries.

Types of rebars:

1-simple rebar: the surface of these rebars is flat that are represented with this symbol Φ, its compressive and tensile strength is 23 kilogram per square millimeter.

2-Ribbed rebar: the surface of these rebars is ribbed in different shapes and its compressive and tensile strength is 32 kilogram per square millimeter that are represented with this symbol Φ.

Note 1: the rebars are available from 6, 8, 10 to 50 mm diameter.

Note 2: the rebars that are with less than 6 mm are called as wire.

Note 3: the rebars with 6 to 12 mm diameter are used for building stirrup and the rebars with 10 to 50 mm diameter are used for building beams, columns, slabs (ceilings), foundations and etc.

Types of ribbed rebars:

3-Complex ribbed rebar: the compressive and tensile strength of these rebars is more than simple and ribbed rebars that it represents with this symbol Φ.

Rebars end bending

Objective: rebars end bending is for better and proper appealing of rebar in the concrete.

The minimum measures for 180 degrees bending.

D- At least equal to 6d for 20 score and less than it.

D- At least equal to 8d for more than 20 and less than 30 scores.

D- At least equal to 10d for more than 30 scores.

The minimum measures for 90 degrees bending.

D- At least equal to 7d for 20 score and less than it.

D- At least equal to 8d for more than 20 and less than 30 scores.

D- At least equal to 10d for more than 30 scores.

 

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