Deformation of non-fully cracked members which are subjected mainly to flexure, α
Eurocode 2 part 1-1: Design of concrete structures 7.4.3 (3)
The deformation may be estimated as follows:
α = ζ α_{II} + (1 - ζ) α_{I} | (7.18) |
where:
- α
- is the deformation parameter considered which may be, for example, a strain, a curvature, a rotation, (or a deflection as a simplification, see the calculation of shrinkage curvatures).
- α_{I}, α_{II}
- are the values of the parameter calculated for the uncracked and fully cracked conditions respectively
- ζ
- is a distribution coefficient (allowing for tensioning stiffening at a section) given by:
ζ = 1 - β (σ_{sr}/σ_{s})^{2} (7.19) with:
- ζ = 0 for uncreacked sections
- β
- a coefficient taking account of the influence of the duration of the loading or of repeated loading on the average strain
= 1,0 for a single short-term loading
= 0,5 for sustained loads or many cycles of repeated loading - σ_{s}
- the stress in the tension reinforcement calculated on the basis of a cracked section
- σ_{sr}
- the stress in the tension reinforcement calculated on the basis of a cracked section under the loading conditions causing first cracking
- Note:
- σ_{sr}/σ_{s} may be replaced by M_{cr}/M for flexure or N_{cr}/N for pure tension, where M_{cr} is the cracking moment and N_{cr} is the cracking force.
This application calculates the deformation α from your inputs.