Resistance to spalling (hollowcore)

The control is carried out for the first load combination in SLS for each chain of dependence, usually those marked "Release." Formulas to consider are those from EN1168 4.3.3.2.1.

The general control states that the spalling stress (σ_sp) must not exceed the spalling capacity (f_ct).

where:

f_ct       Value of the tensile strength of the concrete from the current load combination (see above)

P₀      Initial prestressing force just after release in the considered web

b_w      Thickness of the individual web

e₀      Eccentricity of the prestressing steel

l_pt1     Lower design value of the transmission length

k        Core radius equal to the ratio of the section modulus of the bottom fibre and the net area of the cross section (W_b/A_c)