Design of a T-beam - Reinforced Concrete with FRP Bars: Mechanics and Design - page 270

Design flexural strength: The effective concrete compressive strain at
failure as a function of the neutral axis depth, x, is

ε

cu

⋅ yif ρ≥ρ

f2 fb2

x

( )

ε x,y : =

c2

ε

fu

dx yif

⋅ ρ<ρ

f2 fb2

−

f2

The effective tensile strain in the first layer of FRP reinforcement as a
function of the neutral axis depth, x, is

ε if ρρ

ε

<

fu f2 fb2

ε (x) :

= f2I

( )

cu

f_min2 ⋅ dx, −ε if ρ≥ρ

f2I fu f 2 fb2

x

The compressive force in the concrete as a function of the neutral axis
depth, x, is

( )

ε− ε

x,x
x

( )

c2

⋅φ + s if ρ <ρ ∧ N > 0

fu f_bar f_min2 f 2 fb2 bar2II

ε (x) :

= ε

ε− ε

( ) ( )

f2II

cu cu

f_min2 ⋅ dx, − ⋅φ + s if ρ≥ρ∧ N > 0

f2II fu f_bar f_min2 f 2fb2 bar2II

x x

0otherwise

The compressive force in the concrete as a function of the neutral axis
depth, x, is

ε (x,y)

c2

2" ⋅σ ⋅

c

x

ε

∫

c0

C x) :b = ⋅ psidy

c2

eff

2

ε (x,y)

0in

c2

1 +

ε

c0

The tensile force in the first layer of FRP reinforcement as a function of
the neutral axis depth, x, is

T f2I (x) := A f2I ·E f ·ε f2I (x)

The tensile force in the second layer of FRP reinforcement as a function
of the neutral axis depth, x, is