# Beam Required and Design Strength per ACI 318-19 with ideCAD

How does ideCAD concrete beam required, and design strength according to ACI 318-19?

• Beam required strengths are calculated automatically.

• Beam design strengths are calculated automatically.

Notation

Ag = gross area of concrete section, in2
Av = area of shear reinforcement within spacing s, in.2
fc' = specified compressive strength of concrete, psi
fyt = specified yield strength of transverse reinforcement, psi
Mn = nominal flexural strength at section, in.-lb
Mu = factored moment at section, in.-lb
Pn = nominal axial compressive strength of member, lb
Pu = factored axial force; to be taken as positive for compression and negative for tension, lb
Tn = nominal torsional moment strength, in.-lb
Tu = factored torsional moment at section, in.-lb
U = strength of a member or cross section required to resist factored loads or related internal moments and forces in such combinations as stipulated in ACI 318-19
Vn = nominal shear strength, lb
Vu = factored shear force at section, lb
ϕ = strength reduction factor

### Required Strength

The required strength is calculated in accordance with the factored load combinations in Load Factors and Combinations per ACI 318-19 with ideCAD title.

According to ACI 9.4.2.1 and 9.4.3.1, for beams built integrally supports, Mu and Vu at the support can be calculated at the face of support.

According to ACI 9.4.3.2, if all three conditions given below are satisfied, sections between the face of support and a critical section located d from the face of support for beams shall be permitted to be designed for Vu at that critical section.

• Support reaction, in the direction of applied shear, introduces compression into the end region of the beam

• Loads are applied at or near the top surface of the beam

• No concentrated load occurs between the face of support and the critical section

According to ACI 9.4.4.3, sections between the face of support and a critical section located d from the face of support can be designed for Tu at that critical section, except that there is a concentrated torsional moment within this distance.

### Design Strength

Design strength in all sections should satisfy all conditions given below;

• ϕPn ≥ Pu

• ϕMn ≥ Mu

• ϕVn ≥ Vu

• ϕTn ≥ Tu

Strength reduction factors ϕ is determined according to using ACI Table 21.2.2. Interaction between load effects is considered.

For cases with Pu< 0.10fc’Ag, axial forces are ineffective in nominal flexural strength Mn. If Pu< 0.10fc’Ag, nominal flexural strength Mn with zero compression is calculated in accordance with Flexural Strength per ACI 318-19 with ideCAD title. If Pu≥ 0.10fc’Ag, combined axial and flexural strength, Pn and Mn, are calculated in accordance with Axial strength or Combined Flexural and Axial Strength per ACI 318-19 with ideCAD title.

Nominal shear strength, Vn, is calculated in accordance with One-Way Shear Strength per ACI 318-19 with ideCAD title.

Nominal torsional moment strength, Tn, is calculated in accordance with Torsional Strength per ACI 318-19 with ideCAD (v12) title.