Figure 3.16. Derivation of rectangular stress block from bilinear stress block for a cross section width in the direction of the extreme compression fibre

Similar type of calculations has been carried out for this case. Fig. 3.17 shows for an | as a function of the concrete strength. Three cases are considered:

- the calculated relations for a rectangular cross-section

- the calculated relations for a triangular cross-section with the top at the extreme compressive strain

- the design equation, derived for the case of the rectangular cross-section.

It is shown that the design equation for A is safe for both cases. However, the values for | for the triangular case are lower than the design values.

It is sufficient to reduce the values for i with 10% in order to cover as well the triangular case.

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