Resistance to spalling (hollowcore elements)
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 (σsp) must not exceed the spalling capacity (fct).
where:
fct is the value of the tensile strength of the concrete from the current load combination (see above)
P0 is the initial prestressing force just after release in the considered web
bw is the thickness of the individual web
e0 is the eccentricity of the prestressing steel
lpt1 is the lower design value of the transmission length
k is the core radius equal to the ratio of the section modulus of the bottom fibre and the net area of the cross section (Wb/Ac)