Design of a column - Reinforced Concrete with FRP Bars: Mechanics and Design - page 347

Axial strength is

N1
f

−

∑ (

)

( ) () ()

P:0.85 fb0.8c = ⋅ ′ ⋅⋅ ⋅ + AiE ⋅ ⋅ ε if5 n4 c 4

f f f4

i0 =

P n4 = 91·kip

Flexural strength

N1 − f

∑

h
2

+

h
2

( ) ( )

() ()

M:0.85 fb0.8c = ⋅ ′ ⋅⋅ ⋅ ⋅ −⋅ 0.4c AiE ⋅ ⋅ε if5 ⋅ − d(i)

n4 c 4 4 f f f4 f

i0 =

M =⋅ 266 kipft ⋅ n4

Strength reduction factor

( )

ε N1

2

−

f4 f

0.65 if 1.15 − ≤ 0.65 φ = 0.65

4

ε

fu

( )

ε N1

2

−

f4 f

φ= : 1.15 −

4

ε

fu

( )

ε N1

2

−

f4 f

0.75 if 1.15 − ≥ 0.75

ε

fu

9.5.5 Point 5—Neutral axis at the level
of the highest section fibers

ε fu = 0.01

The strain in FRP reinforcement is

−ε

()

fu

ε (i): ⋅ di

=

if5

( )

f

dN 1 −

f f