Design of column strengthening with CF sheets - Strengthening of Concrete Structures with Adhesively Bonded Reinforcement - page 106

1992-1-1 or the DAfStb guideline [1, 2] are also used. As the failure of confined
compression members within the scope of applicability of the DAfStb guideline [1, 2]
can be attributed to the failure of the CF sheet, the expression for the load-carrying
capacity of the confined concrete is reduced by the corresponding partial safety
factor γ LG .

The load-carrying capacity of a reinforced concrete column having a circular cross-
section, a rotationally symmetrical arrangement of reinforcing steel and a wrapping of
CF sheet can therefore be determined on the basis of the moment axial load

interaction, which is determined using the two equations below for calculating the
resistances of the member. The first equation describes the axial load capacity
N Rd and the second the associated moment capacity M Rd according to second-order
theory.

-

1
γ LG ? θ ? α 1 ? f cck ? A c ?

sin 2 ? π ? θ 1

γ s ? θ c θ t

N Rd 1 ? f yk ? A s (7.37)

2 ? π ? θ

!

2
? ξ 1 ? ξ 2 ? ϕ bal ? K φ

l 0
π

M Rd N Rd ? e tot

sin 3 1

γ LG ?

2
3 ? α 1 ? f cck ? A c ?

D
2 ?

π ? θ

π

1
γ s ? f yk ? A s ?

D
2 ?

sin π ? θ c sin π ? θ t

(7.38)

π

where:
θ relative angle describing the position of the stress block in the cross-section:

0 θ 1

γ LG partial safety factor for surface-mounted CF sheet at the ultimate limit state

α 1 stress block geometry factor.

f cck
f ck

α 1 1 : 17 0 : 2 ? (7.39)

f cck characteristic compressive strength of con ned concrete.

2
4

3
5

! 2

s 2

?

D c

f cck f ck k ? E jl ? ε juk ρ wy ? f wyk Δ p (7.40)

D

f ck compressive strength of concrete subjected to uniaxial loading

E jl relative stiffness of confining reinforcement made from CF sheet.

2 ? E L ? t L
D

E jl (7.41)