2.3.6 Determining the Required Reinforcement

Determining the Required Reinforcement

To determine the dimension of the necessary reinforcement area, the design axial force to be resisted n_φ is divided in the respective reinforcement direction φ by the steel stress at the yield point.

The steel stress at the yield point is defined differently depending on the standard and type of concrete. Furthermore, for the design, the respective partial safety factor for the reinforcing steel has to be considered.

If the reinforcement is under compression instead of tension, the steel stress for the allowable concrete compression at failure is to be determined. It is the same in all standards and equals 2 ‰. Thus, the steel stress can be determined by using the modulus of elasticity as follows:

$\sigma = E_s · 0.002$

Should the steel stress be greater than the steel stress at the yield point, the steel stress at the yield point is used. Apart from that, a compression reinforcement is only determined if the resistant axial force n_strut,d per meter of the concrete is smaller than the acting, compression-inducing design axial force. The compression reinforcement is then designed for the difference of the two axial forces.