Example 3: Column strengthening - Strengthening of Concrete Structures with Adhesively Bonded Reinforcement - page 127

8.6 Serviceability limit state
In order to avoid unacceptable damage to the concrete microstructure at the service-
ability limit state, DAfStb guideline [1, 2] part 1 section 7.2 (RV 15) specifies that the
theoretical thickness of confining reinforcement necessary t L must comply with the
following condition according to DAfStb guideline [1, 2] part 1 Eq. (RV 7.5):

D
2 ? E L ? ε juk ?

1
k

A s
A c ? ε c2

t L ? γ LG ? γ F ? k k ? f ck ? α cc ? f ck

j ? E s j

f ck

f syk
γ s

A s
A c

?

500
2 ? 230 000 ? 1

1
2 : 0 ?

t L 1 : 35 ? 1 : 43 ? 0 : 89 0 : 0044 ? 30

?

863 ? 10 3 :

30

9
1964 ? 2

58 : 500

1 : 15 ?

9
1964

58 :

0 : 85 ? 30 : 0 ? 200 ?

t L 2 : 12 mm

In this equation the permissible compressive strain in the concrete ε c2 was determined
according to DIN EN 1992-1-1 [20] Table 3.1 and the reduction factor for uniaxial
concrete compressive strength α cc = 0.85 to DIN EN 1992-1-1/NA [21] section 31.6 (1).
In addition, the weighted partial safety factor γ F for actions was calculated according to
the contributions of the permanent and variable actions for the governing combination of
forces and moments at the ultimate limit state:

N Ed
G k Q k

8
2014 : 7 2500

6469 :

γ F 1 : 43

As the thickness of con ning reinforcement used is less than the maximum permissible
thickness according to DAfStb guideline [1, 2] part 1 Eq. (RV 7.5), the design for
serviceability is satisfactory.
t L 0 : 75 mm t L ; max 2 : 12 mm