Maximum concrete stresses

As the beam is a T-section, the values of Wx and Wb are not equal. By calculation it can be shown that I = 6.79 x 109 mm4 and that the centroid of the section is at a height of 196 mm from the soffit.

Therefore

The calculation of the stresses under each load combination is not shown here. The method follows that given in the Post tensioned concrete floors: Design handbook. The top and bottom concrete stress for transfer conditions are given in Table 9.3 and those after all losses are given in Table 9.4.

Table 9.3 Stresses at transfer

Zone

Top stresses, f (N/mm2)

Bottom stresses, f (N/mm2)

max.

min.

max.

min.

0 0

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