using formulas, graphs and engineering sciences
The rules on iron strength dimensions and standards for building structures are regulated in SNI (Indonesian National Standard). Iron sold in the market also many do not have SNI standard, this can doubt the strength of iron tug.
but this constraint is related when working on the reinforcement of steel in the field work, that is when grafting steel reinforcement. Improper grafting will make the strength of the reinforcing steel low. The reinforcement of steel reinforcement shall be in accordance with the SNI of 40D (40 times the diameter of reinforcement).
each in the iron connection also needs to be given a little bending to iron joints become more solid and increase the tensile strength of the reinforcement. in the drawings of this plan should also be mentioned the details of the connection, bengkokan and dimensions are clear.
below there is an example of a minimum length calculation for steel reinforcement connections as below:
Is known:
Reinforcement diameter = ( Ø 16 mm )
Asked: Minimum reinforcement length ( ........ ? )
Answer:
- Minimum length of reinforcing joints = 40 x Diameter (Ø)
- Minimum length of reinforcing joints = 40 x Ø16 mm
From the stress-strain relation of the reinforcing steel, the angle α (alpha) is defined, ie between the straight line curve drawn from the zero voltage state to the melting stress (fy) and the strain line (εs).
The modulus of elasticity of the reinforcing steel (Es) is the tangent of the angle α (alpha). According to Section 10.5.2 of SNI 03-2847-2002, the modulus of elasticity of non-Prestressed steel reinforcement may be taken up to 20000 MPa.
this photograph as an example of the connection of iron diameter 12mm to the SNI national standard of indonesia, and also in accordance with the rules of civil engineering Sciences that have been set by the experts and engineers of genius research.
by. 
I understand another reason why the basic theory for tensile strength and tensile iron steel is based on the regulations of SNI. Please read this source: