Design of column strengthening with CF sheets - Strengthening of Concrete Structures with Adhesively Bonded Reinforcement - page 109

2 ? t L ? E L ? ε juk
D

p 1 (7.55)

p 2 transverse compressive stress due to the confining effect of the CF sheet and the

transverse reinforcing steel.

p 1 ? c

2 ? t L ? E L ? ε juk t w ; eff ? f wyk

p 2 (7.56)

D c c

f ck * point at which projected straight part of curve intersects stress axis.

0
@

1
A

s w
2

2

D c

?

f ck f ck k 1 ? ρ wy ? f wyk Δ p (7.57)

D

A c gross cross-sectional area of concrete in reinforced concrete column

γ s partial safety factor for reinforcing steel at ultimate limit state

θ c relative angle describing the stress distribution in the distributed longitudinal

reinforcing steel subjected to compression: 0 θ c = 1.25 θ 0.125 1

θ t relative angle describing the stress distribution in the distributed longitudinal

reinforcing steel subjected to tension: 0 θ t = 1.125 1.5 θ 1

f yk characteristic yield strength of longitudinal reinforcing steel

e tot eccentricity of loading according to rst-order theory: e tot = e 0 + e i

e 0 intentional eccentricity of loading according to rst-order theory

e i additional unintentional eccentricity of loading to DIN EN 1992-1-1

l 0 buckling length of compression member

ξ 1 factor to allow for the decrease in curvature for a rise in the compressive force N Rk

beyond N bal .

0 : 8 ? f cck ? A c N bal

N Rk

ξ 1

N Rd ? γ LG 1

(7.58)

ξ 2 factor to allow for the geometry of the compression member and the strain in the

con ning reinforcement.

l 0
D 1

ξ 2 1 : 15 0 : 06 ? ρ ε 0 : 01 0 : 012 ? ρ ε ? (7.59)

ρ ε strain coefficient.

ρ ε ε juk
ε c2

(7.60)

ε c2 longitudinal strain in concrete subjected to uniaxial compression upon reaching

compressive strength: 0.002

D diameter of reinforced concrete column
ϕ bal maximum curvature.

ε c2 =

ε cu ε yk
D D c 2 ? ϕ w ϕ s

ϕ bal 2 ? (7.61)