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, E_c, and Shear Modulus is calculated automatically according to the selected material's design property.

Notation

E_c = modulus of elasticity of concrete, psi
E_s = modulus of elasticity of reinforcement, psi
f_c^' = specified compressive strength of concrete, psi
f_y = specified yield strength for nonprestressed reinforcement, psi
ε_s = strain value of reinforcement
ε_y = yield strain of reinforcement
w_c =density, unit weight, of normal weight concrete, lb/ft³

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Concrete Design Properties

Specified compressive strength

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

Application	Minimum f_c', 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 E_c, 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 f_y is equal to E_s times ε_s which is the value from the strain diagram at the location of the reinforcement. For strains greater than that corresponding to f_y, stress is constant and equals f_y.

The modulus of elasticity, E_s, 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, f_c^', and specified yield strength for reinforcement f_y 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
f_c^' = 3000 psi	f_c^' = 21 MPa	f_c^' = 210 kgf/cm²	Concrete
f_c^' = 4000 psi	f_c^' = 28 MPa	f_c^' = 280 kgf/cm²
f_c^' = 5000 psi	f_c^' = 35 MPa	f_c^' = 350 kgf/cm²
f_c^' = 6000 psi	f_c^' = 40 MPa	f_c^' = 420 kgf/cm²
f_y = 40,000 psi	f_y = 280 MPa	f_y = 17,600 kgf/cm²	Reinforcement
f_y = 60,000 psi	f_y = 420 MPa	f_y = 19,000 kgf/cm²	Reinforcement

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