Design of square footing for a single column - Reinforced Concrete with FRP Bars: Mechanics and Design - page 375

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:

w lim = 0.02·in. Crack width limit

FRP ultimate design properties: The ultimate design properties are cal-
culated per Section 7.2 of ACI 440.1R-06:

f fu := C E ·f fuu = 49·ksi Design tensile strength

ε fu := C E ·ε fuu = 0.0086 Design rupture strain

FRP creep-rupture limit stress: The FRP creep-rupture limit stress is cal-
culated per Section 8.4 of ACI 440.1R-06:

f f _ creep := k creep ·f fu = 9.8·ksi

Minimum FRP reinforcement ratio: The minimum FRP reinforcement
ratio, ρ f,smin , to limit cracks due to shrinkage and temperature is given by
Equation (10-1) of ACI 440.1R-06 (computed in step 3):

ρ fsmin := ρ f _ ts = 0.0036

The following minimum clear concrete cover is selected:

c c := 2.0 in.

The effective reinforcement depth is

3 ⋅φ

f_bar

d: hc =−− = inf ⋅ .

c

f

2

As a starting point for the design, the FRP reinforcement area can be
taken equal to 1.5 times the minimum FRP reinforcement area:

Af_ f_min := (b·d f )·1.5ρ fsmin = 17. 0 85·in. 2

The number of FRP bars can be estimated as follows:

A
A

f_min

N : = = 13.487

barEstimated

f_bar

The number of bars is therefore:

N bar := 14

A f := N bar ·A f_bar = 17.735·in. 2