Function
Perform cracked section analysis for checking the cracking deflection in meshed slabs.
Note 1
Cracked section analysis is carried out in the post-processing mode after completing elastic analysis.
Note 2
Cracked section analysis is carried out when the load combinations are selected in Deflection (Cracked) field in Slab/Wall/Shell Load Combinations.
in case of Eurocode, Quasi-permanent type serviceability load combination can be selected in Deflection (Cracked) field. Serviceability load combination type can be classified in Serviceability Load Combination Type into Characteristic, Frequent, or Quasi-permanent.
Note 3
Cracking deflection can be checked in Slab Serviceability Checking. Members which are expected to crack, but may not be fully cracked, will behave in a manner intermediate between the uncracked and fully cracked conditions and, for members subjected mainly to flexure, an adequate prediction of behavior is given by the following expression based on the sub clause 7.4.3 (3) in EN 1992-1-1:2004. Following factors including the effective moment of inertia by elements for each iteration step can be checked in "File Name_CSA.OUT" file.
Therefore Ieff (effective moment of inertia) can be calculated from the following equation.
Where,
Note 4
The flexural rigidity of a beam may not be constant along its length because of varying amount of steel reinforcement and cracking at different sections along the beam. According to ACI Code 9.5.2.2 and 9.5.2.3, short-term deflection is computed using elastic methods of analysis considering effects of cracking and reinforcement on member stiffness, with the modulus of elasticity for concrete Ec=15100 √f’c and with the effective moment of inertia Iegiven as follows, but not greater than Ig.
and the cracking moment Mcr is given in the below Eq.
Ma = maximum moment in member at stage deflection is computed
Ig = moment of inertia of gross concrete section about centroidal axis, neglecting reinforcement
Icr = moment of inertia of cracked section transformed to concrete
fr = modulus of rupture of concrete = c 2 f ¢
yt = distance from centroidal axis of gross section, neglecting reinforcement, to extreme fiber in tension.
Moment of inertia of cracked section about neutral axis,
Call
From the Main Menu select [Design] tab > [Type : Meshed Design] > [Perform/Result] group > [Cracked Section Analysis Control] > [Perform Cracked Section Analysis]