Spread footing - minimum reinforcement expression

[Mirko.Jurcevic]

For my spread footing, Robot calculates minimum reinforcement as:

4,17cm2/m' for bottom zone, and 3,14cm'/m' for top.

According to EN 1992-1-1, this values should be calculated as:

As,min = 0.0013⋅bt⋅d = 0.0013⋅100⋅44 = 5.72 cm2

or 

As,min = 0.26⋅(fctm/fyk)⋅bt⋅d = 0.26⋅0.22/50.00⋅100⋅44 = 5.03 cm2

whichever is greater.

??

Question is simple: Which expression Robot uses to calculate minimum reinforcement of the spread footing?

Same question here (a week ago):

http://forums.autodesk.com/t5/Robot-Structural-Analysis/minimum-reinforcement-of-foundation/td-p/306...

but it seems nobody saw it.

[Rafal.Gaweda]

It is being checked.
I will let you know asap.

[Mirko.Jurcevic]

Thanks Rafal.

[Rafal.Gaweda]

2015 Results 

[Mirko.Jurcevic]

Ok,

it seems that Robot 2015 got it right (for C20/25 and d=43cm)

As,min = 0.0013⋅bt⋅d = 0.0013⋅100⋅43 = 5.59 cm2

But what's with 2014 version users?

[Mirko.Jurcevic]

And what's with that bending moment, minimal reinforcement is not relevant in that case, look, for bigger bending moment:

Design value of concrete compressive strength:

fcd = αcc⋅fck/γC = 1.00⋅2/1.5 = 1.33 kN/cm2

Design yield strength of reinforcement:

fyd = fyk/γS = 50/1.15 = 43.48 kN/cm2

Effective depth of a cross-section:

d = h - d1 = 50 - 7 = 43 cm

Value of nondimensional bending moment:

μEd = MEd/(b⋅d⋅fcd) = 17250/(100⋅432⋅1.33) = 0.070

For:   μRd = 0.070

εc = 2.3 ‰         εs1 = 20.0 ‰         ξ = 0.103         ζ = 0.960

Required reinforcement:

As1 = MEd / (fyd⋅ζ⋅d) = 17250 / (43.48⋅0.960⋅43) = 9.61 cm2

As1 = 9.61 cm2

Minimum reinforcement:

As,min = 0.0013⋅bt⋅d = 0.0013⋅100⋅43 = 5.59 cm2

Maximum reinforcement:

As,max = 0.04⋅b⋅h = 0.04⋅100⋅50 = 200.00 cm2

As,min = 5.59 cm2 < As1 = 9.61 cm2 < Amax = 200.00 cm2

Relevant required reinforcement:

As,req = 9.61 cm2