# Concrete and Reinforcement Materials per ACI 318-19 with ideCAD

How does ideCAD define concrete and reinforcement materials according to ACI 318-19?

• Design properties for concrete and reinforcement materials are selected by the user.

• Modulus of elasticity, Ec, and Shear Modulus is calculated automatically according to the selected material's design property.

Notation

Ec = modulus of elasticity of concrete, psi
Es = modulus of elasticity of reinforcement, psi
fc' = specified compressive strength of concrete, psi
fy = specified yield strength for nonprestressed reinforcement, psi
εs = strain value of reinforcement
εy = yield strain of reinforcement
wc = density, unit weight, of normal weight concrete, lb/ft3

### Concrete Design Properties

Specified compressive strength

The compressive strength of the concrete material used in reinforced concrete elements is shown with fc'. ACI defines a minimum value of fc' for structural concrete, with no limit for the maximum value. Limit values for fc' are shown in ACI Table 19.2.1.1.

Application

Minimum fc', psi

General

2500

Foundations for structures assigned to SDC A. B. or C

2500

Foundations for Residential and Utility use and occupancy classifications with stud-bearing wall construction two stories or less assigned to SDC D, E, or F

2500

Foundations for structures assigned to SDC D, E, or F

3000

Special moment frames
Special structural walls with Grade 60 or 80 reinforcement

3000

Special structural walls with Grade 100 reinforcement

5000

Modulus of Elasticity

The modulus of elasticity Ec, for concrete, is calculated as shown in ACI Equation 19.2.2.1.b.

### Nonprestressed Reinforcement Bars Design Properties

For non-prestressed reinforcement bars, the stress value below fy is equal to Es times εs which is the value from the strain diagram at the location of the reinforcement. For strains greater than that corresponding to fy, stress is constant and equals fy.

The modulus of elasticity, Es, for nonprestressed reinforcement bar, is 29,000,000 psi.

Information on sizes and areas of various ASTM standard steel reinforcement is presented below in U.S. Customary and SI-METRIC units.

Bar size, no.

Nominal diameter, in

Nominal area, in2

Nominal diameter, mm

Nominal area, cm2

#2

0.25

0.05

6.350

0.32

#3

0.375

0.11

9.525

0.71

#4

0.500

0.20

12.700

1.27

#5

0.625

0.31

15.875

1.98

#6

0.750

0.44

19.050

2.85

#7

0.875

0.60

22.225

3.88

#8

1.000

0.79

25.400

5.07

#9

1.128

1.00

28.651

6.45

#10

1.270

1.27

32.258

8.17

#11

1.410

1.56

35.814

10.07

#14

1.693

2.25

43.002

14.52

#18

2.257

4.00

57.328

25.81

Equivalence Between U.S. Customary Units, SI-METRIC, and MKS-METRIC of specified compressive strength, fc', and specified yield strength for reinforcement fy are shown below.

U.S. Customary units stress in pounds per square inch (psi)

SI-metric stress in MPA

mks-metric stress in kgf/cm2

fc' = 3000 psi

fc' = 21 MPa

fc' = 210 kgf/cm2

Concrete

fc' = 4000 psi

fc' = 28 MPa

fc' = 280 kgf/cm2

fc' = 5000 psi

fc' = 35 MPa

fc' = 350 kgf/cm2

fc' = 6000 psi

fc' = 40 MPa

fc' = 420 kgf/cm2

fy = 40,000 psi

fy = 280 MPa

fy = 17,600 kgf/cm2

Reinforcement

fy = 60,000 psi

fy = 420 MPa

fy = 19,000 kgf/cm2