Calculation of crack width

EuroCode - EN 1992-1-1 -

Author: Design Forms s.r.o.

Created: 10/20/2016

Last updated: 10/20/2016

Description:

Calculation of crack width
Annotation:

Stress in the reinforcement s_{s1 } may be defined by calculation from bending moment M_{Ed}

or it can be set manually (when M_{Ed} = 0).

And _{p‘} is area beforehand of afterwards stressed reinforcement in area A_{c,eff}

A_{c,eff} effective area of tension concrete surrounded by reinforcement of prestressed reinforcement in height h_{c,ef} (see image 7.1)

h_{c,ef} is smaller from:

- 2,5(h - d)
- (h - x)/3
- h/2

a) beam

b) plate

c) member in tension

[A] - center of gravity of reinforcement

[B] - effective tension area, Ac,eff

[C] - effective tension area near top suface, Acb,eff

x is ration of strength of prestressed reinforcement and reinforcement according to the table 6.2 in 6.8.2:

k_{1} is coefficient of coherent parameters of reinforcement:

= 0,8 bars with big cohesion;

= 1,6 bars with smooth surface (e.g. presstresing bars);

k_{2} is coefficient of ratio of deformation :

= 0,5 for bending;

= 1,0 for simple tension.

In cases of eccentric tension or local areas - the values k_{2}should be used, it is calculated by this formula:

k_{2} = (e_{1} + e_{2})/2e_{1}

where e_{1} is bigger ande_{2} is smaller tension deformation ratio on edges of cross section, which is weakened by crack.

Values k3 and k4, which are used may be found in the nationa annex. The recommended values in Czech Republic (see NA 2.74):

k3 = 3,400

k4 = 0,425.

[A] - neutral axis

[B] - surface of tensioned concrete

[C] - expected crack width according to (7.14)

[D] - expected crack width according to (7.11)

[E] - real crack width