# First moment of area of the reinforcement (Eurocode 2)

QUESTION

I would like to have your opinions on the following issue:

I’ve seen someone who calculated the first moment of area of the reinforcement about the centroid of the section, using the following formula:

S = -Asc (yc - d2) + Ast (d -yc)
where:
S = first moment of area of the reinforcement
Asc = area of steel in compression
Ast = area of steel in tension
d = effective section depth (from top fibre to tension steel)
d2 = concrete cover of compression steel
yc = distance from extreme compressive fibre to neutral axis

My question is: whether the minus sign ("-") in front of Asc was correct?
Should it be + ? If it is correct, why would we need to subtract the compression steel component?

I need to find a correct equation to calculate S to use Clause 7.4.3 (6) Eurocode 2.

REPLIES

avscorreia
As shrinkage curvature occurs when there’s a difference between the top and bottom reinforcement, the area module that is calculated takes this effect into account by considering the effect of the top reinforcement with a negative sign.

SOURCE
Above is a snippet.

Thank you.

Sorry, but no.