Strengthening of Columns for Confinement - Strengthening Design of Reinforced Concrete with FRP - page 178

2. The depth of each layer measured from the top extreme fiber is

t t 21

2

i −

lr lr

d = , d = + t , d = × t (7.33)

lr 1 lr 2 lr lri lr

2 2

3. The angle of each layer measured from the vertical axis is

θ= Dd
D

/2

lri

cos

(7.34) lri

/2

4. The width of each layer ( i ) is

bD
lri

=×θ sin

(7.35) lri

5. The depth of the neutral axis ( c ) measured from the top extreme fiber is

c = d for point B (7.36)

ε
ε+ε

ccu

cd = for point C (7.37)

ccu sy

6. The depth of the transition point ( d t ) measured from the top extreme fiber is

=−=− ε
ε

t

dcyc
t

1

(7.38) t

ccu

where ε t is computed from Equation (7.5).

7. If dd
lri t , use Equation (7.3b); otherwise, use Equation (7.3a), with

ε= −

cd
c

lri

ε

ccu

(7.39)

ci

and f ci from Equation (7.3).

8. The axial force ( P cn ) and the bending moment ( M cn ) contribution of con-
crete are

∑

=

P f bt cn ci lrilr

i

D

∑

M = f bt × − d (7.4 0)

cn ci lri lr lri

2

i