Design of a T-beam - Reinforced Concrete with FRP Bars: Mechanics and Design - page 258

“OK” if s s
“Too many bars”otherwise

≥

f1_clear f_min1

Check_BarSpacing1 :

=

Check_BarSpacing1 = “OK”

The center-to-center bar spacing is

s f1 := s f1 _ clear + ϕ f _ bar = 4∙in.

Design flexural strength: Based on cross-section compatibility, the effec-
tive concrete compressive strain distribution at failure can be computed as
a function of the neutral axis depth, x:

ε

cu

y f ρ≥ρ

f1 fb1

x

ε (x,y) :

= c1

ε

fu

dx y f

⋅ ρ < ρ

f1 fb1

−

f1

Based on cross-section compatibility, the effective tensile strain in the
FRP reinforcement can be computed as a function of the neutral axis
depth, x:

ε if ρρ

ε

<

fu f1 fb1

ε (x): if ρ≥ρ

=

f1

( )

f1 fb1

cu

min ⋅ dx, −ε

f1 fu

x

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

ε (x,y)

c1

2" ⋅ρ ⋅

c

x

ε

∫

c0

C x) :b ⋅ psidy

=

c1 w

2

ε (x,y)

0in

c1

1 +

ε

c0

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

T f1 (x) := A f1 ∙E f ∙ε f1 (x)