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):
but it seems nobody saw it.
Thanks Rafal.
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?
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
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