The characteristic strength of steel is the steel strength or yield point, which is taken into account in the design of components.
The definition is significantly different from that characteristic strength of concrete It is based on the elastic limit of steel.
Depending on the type of reinforcing bars, the yield strength varies. The variation can be expressed as follows.
- mild steel; f j = 250 N/mm 2
- Steel Gate; f j = 460 N/mm 2
- TMT Rods; f j = 500 N/mm 2
There are also other types of bars whose yield limit is higher than the value indicated above. There are several methods that can be used to determine the characteristic strength of steel. As each material has different stress-strain properties, it is very difficult to determine the yield strength. The following methods can be highlighted as a commonly used method for determining yield strength.
- True elastic limit
- Proportionality limit
- Elastic limit (yield limit)
- Stretch limit
- Displacement yield strength (yield limit) Displacement yield strength is defined by 0.1% or 0.2% plastic strain.
- Upper and lower yield strength
In addition to the methods mentioned above, there are other theoretically developed methods for determining the yield strength. This method is based on material properties. Therefore, there are two types known as isotropic and anisotropic flow criteria. The following methods are used to determine the yield strength in isotropic materials.
- Maximum principal stress theory
- Maximum principal strain theory
- Maximum shear strain theory
- The theory of total strain energy
- Maximum distortion energy theory (Von Mises flow criterion)
- Mohr-Coulomb flow criterion
- Ducker-Prager flow criterion
- Bresler-Pister flow criterion
- William-Warnke flow criterion
There are also theoretical methods to evaluate the yield strength in anisotropic materials. The following methods can be highlighted as follows.
- Hill's quadratic yield criterion
- Hill's Generalized Yield Criterion
- Hosford flow criterion
