how to calculate reinforcement pad dimensions

N Ed should be determined considering the characteristic values of prestress and axial forces under the relevant combination of actions

N Ed is the axial force at the serviceability limit state acting on the part of the cross-section under consideration (compressive force positive).

For rectangular sections and webs of box sections and T -sections:

k c is a coefficient which takes account of the stress distribution within the section immediately prior to cracking and of the change of the lever arm:įor bending or bending combined with axial forces:.

= 0,65 for webs with h ≥ 800 mm or flanges with widths greater than 800 mm = 1,0 for webs with h ≤ 300 mm or flanges with widths less than 300 mm

k is the coefficient which allows for the effect of non-uniform self-equilibrating stresses, which lead to a reduction of restraint forces.

f ct,eff is the mean value of the tensile strength of the concrete effective at the time when the cracks may first be expected to occur:į ct,eff = f ctm or lower, (f ctm(t)), if cracking is expected earlier than 28 days.

A lower value may, however, be needed to satisfy the crack width limits according to the maximum bar size or spacing (see 7.3.3 (2)) This may be taken as the yield strength of the reinforcement, f yk.

σ s is the absolute value of the maximum stress permitted in the reinforcement immediately after formation of the crack.

The tensile zone is that part of the section which is calculated to be in tension just before formation of the first crack

A ct is the area of concrete within tensile zone.A s,min is the minimum area of reinforcing steel within the tensile zone.

How to calculate reinforcement pad dimensions