Design of a two-way slab - Reinforced Concrete with FRP Bars: Mechanics and Design - page 318

Bar location modification factor for top reinforcement with less than
12 in. of concrete below it is

α Neg := 1.0

Required stress in the FRP is

f fr := E f ·ε f (cu) 80·ksi

The developable tensile stress is (ACI 440.1R-06 Equation 11-3):

′ ⋅
α

fpsi

≥

1 C1

c

emb
f_bar

b
f_bar

emb
f_bar

f f ⋅ 13.6 ⋅ φ + ⋅ φ + 340 f =33.677 ksi ⋅

fu fu

φ

if =

Neg

fd

fpsi ′ ⋅

α

1 C1 +340

c emb b emb

⋅ 13.6 ⋅ φ + ⋅ φ otherwise

φ

Neg f_bar f_bar f_bar

“Bar ultimate strength”iff ≥ f

CheckFailure:=

fd fr

“Bond strength otherwise”

CheckFailure = “Bond strength”

The cross section of interest is a bond-critical section. The nomi-
nal moment capacity, therefore, has to be computed per ACI 440.1R-06
Equation (8-5) or ACI 440.1R-06 Equation (8-6b) when the failure mode is
vconcrete crushing or bond, respectively:

1
2

Af
0.85 f

⋅
⋅′

( )

f f

Af mind ,d ⋅ ⋅ −⋅

f fd f1f2

c

m: = if Check Failure=“Boldstrength”

nb

m fCheckFailure=“Bar ultimate strength”

n

ft kip
ft

⋅

m=8.11 ⋅

nb

The maximum ultimate moment at the exterior support is

ft kip
ft

⋅

m:=4.36 ⋅

uNegMax