Design of a T-beam - Reinforced Concrete with FRP Bars: Mechanics and Design - page 261

a f1 = 4.112∙in.

Neutral axis depth is

c: a

f1

= =5.482 in.f1 ⋅

f1

β

1

The nominal moment capacity is

a
2

f1

M: = Af d ⋅ ⋅ − = 401 ft kip ⋅⋅ nACI_1

f1 f1 f1

The concrete crushing failure mode is less brittle than the one due to
FRP rupture. The ϕ-factor is computed according to Equation (8-7) of ACI
440.1R-06:

0.55 if ρ≤ρ = 0.55

f1 fb1

+ ⋅ ρ
ρ

φ : =

f1

0.30 0.25 if ρ<ρ< 1.4 ⋅ρ

bACI _1

fb1 f1 fb1

fb1

0.65 otherwise

The design flexural strength equation is computed per Equation (8-1) of
ACI 440.1R-06:

ϕ bACI _ 1 ·M nACI = 221·kip·ft

( )

“OK”if if φ ⋅ MMM=145 kipft ≥ ⋅ ⋅

nACI _1 u1 u1

bACI _1

Check_FlexureACI_1: =

“Not good”otherwise

Check_FlexureACI_1 = “OK”

Embedment length: Because this is a case of negative reinforcement, it
has to be checked if adequate moment capacity can be achieved at the end
of the embedment length. The available length for embedment is

1 emb1 := 12 in.

The developable tensile stress is calculated per Equation (11-3) of ACI
440.1R-06. Minimum between cover to bar center and half of the center-
to-center bar spacing is

+ φ , s

2

=⋅

f_bar f1

C: minc = 2in c

b1

2