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In the following figure the value of kc is plotted against o for a value of fctf of 2.9 Mpa according to both the above formulation and the equation of prEN.

Figure 7.3. Value of kc as a function of the axial force

Figure 7.3. Value of kc as a function of the axial force

In the next figure the minimum reinforcement for a section subject to a compressive force (expressed in terms of a reduced axial force) is shown calculated according to 4 different methods:

- Proposal of prEN

- Compensation of tension block. This procedure is on the safe side since it neglects the increase of the lever arm which occurs after cracking.

- Direct calculation (exact determination of a)

- Procedure explained above in which a is taken as a constant equal to 0.8.

-prEN 1092-1

Compensate Traction Block

---Direct Calculation

Adimensional Axial Force

Figure 7.4. Comparison of different approximate expressions for the calculation of the minimum reinforcement

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