Design of a one-way slab - Reinforced Concrete with FRP Bars: Mechanics and Design - page 217

The minimum development length is computed according to ACI 440.1R-
06 Equation (11-6):

f
f'

fu

α⋅ − 340

Pos

⋅ psi

c

.

1: = φ= 25.364 in ⋅

d_min

C

f_bar

b2

13.6 + φ

f_bar

The following development length is considered and is available to pro-
vide the required moment capacity:

l d := 26 in.

6.6.3 Case 3—Interior support
Reinforcement required to resist bending moments: The same procedure
discussed for case 1 is followed.
The effective reinforcement depth is

=−− φ

f_bar

d:t c =⋅ 7 n .

f3 slab c

2

ϕ-factor ϕ b _ trial = 0.65

The longitudinal reinforcement ratio required for bending is

M 1

bd

( )

u3

ρ : = ⋅ 0.00292 M7kipft =⋅ ⋅

f_req_bend3 u3

β ⋅

1

φ⋅ f ⋅ d 2 ⋅ 0.15d

f3

b_trial fu f3 f3

The minimum reinforcement requirement has to be verified. Equation
(8-8) of ACI 440.1R-06 is used. If the failure is not governed by FRP rup-
ture, this requirement is automatically achieved:

4.9fpsi
f

⋅ ′ ⋅

bd , 300psi
f

c

( )

2

A: = ρf_min3) ⋅ bd ⋅ = 0.315 in ⋅

f_min3 f3 f3

fu fu

A
bd

f_min3

ρ : = = 0.00375

f_min3

⋅

f1

The design reinforcement ratio required for bending is taken as

ρ f_bend3 := max (ρ f_red_bend3 , ρ f_min3 ) = 0.00375

Reinforcement required for concrete shear strength: The same procedure
discussed for Case 1 is followed.