Design of square footing for a single column - Reinforced Concrete with FRP Bars: Mechanics and Design - page 380

The ratio of modulus of elasticity of bars to modulus of elasticity of
concrete is

E
E

f

n: == 1.399

f

c

The ratio of depth of neutral axis to reinforcement depth, calculated per
Equation (8-12), is

2

( )

k: =ρ⋅ 2 n + ρ⋅ n ρ⋅ n=0.119

f f_des f f_des f f f

with ρ fdes = 0.00561

The tensile stress in the FRP is

M

creep

f : = =6.2 ksi ⋅

fcreep

k
3

f

Ad 1 ⋅⋅ −

f f

“O K” if f ≤ f (f =⋅ 9.8ksi)

fcreep f_creep f_creep

Check_Creep: =

“Not good”otherwise

Check_Creep = “OK”

10.8 STEP 6—CHECK CRACK WIDTH

Crack width is checked using Equation (8-9) of ACI 440.1R-06. A crack
width limit, w lim , of 0.020 in. is used for exterior exposure. The ratio of
modulus of elasticity of bars to modulus of elasticity of concrete is

n f = 1.399
The ratio of depth of neutral axis to reinforcement depth is

k f = 0.119
Tensile stress in GFRP under service loads is

M

sMax

f: = =⋅ 9.1ksi

fs

k
3

f

Ad 1 ⋅⋅ −

f f

with M sMax = 337.7 · kip · ft.