Design of a T-beam - Reinforced Concrete with FRP Bars: Mechanics and Design - page 262

Bar location modification factor for top reinforcement is

α Neg1 := 1.5

Required stress in the FRP is

f fr1 := E f ·ε f1 (c u1 ) = 64·ksi

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

fpsi ⋅ 1 C 1

c

emb1
f_bar

b1
f_bar

emb1
f_bar

f f ⋅ 13.6 ⋅ φ + φ ⋅ φ + 340 ≥= f 27.2ksi ⋅

fu fu

α

Neg1

f : =

fd11

f' ⋅ psi

1 C 1

c

emb1 b1 emb1

⋅ 13.6 ⋅ φ + φ ⋅ φ + 340 otherwise

α

Neg1 f_bar f_bar f_bar

“Bar ultimate strength”iff ≥ f

fd11 fr1

CheckFailure1 : =

“Bar strength” therwise

CheckFailurel = “Bondstrength”

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

1
2

Af
0.85 fb

⋅
⋅ ′ ⋅

f1 f1

Af ⋅ ⋅ d −⋅ if CheckFailure Bond strength” =

f1 fd11 f1

M

: =

c w

n1b1

MifcheckFailure = “Bar ultimatestrength”

n1

M n1b1 = 175·ft·kip

The ultimate moment is

M u1 = 145·ft·kip

The strength-reduction factor when failure is controlled by bond is

0.55 if CheckFailure1 Bond strength” .55 = =

φ : =

b1_ bond

φ if CheckFailure1“Barultimatestrength” =

b1