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

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

• Wall required strengths are calculated automatically.

• Wall 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
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.

Reinforced concrete walls with rectangular, I, T, L, U, or C crosssections are modeled with finite elements (shells) containing degrees of freedom for both in-plane and out-of-plane displacements. The resultant of the finite element joint forces are obtained as equivalent internal force (Mu, Pu) at the cross-section gravity center, based on shear wall required strength and design strength calculations.

The wall shear design is applied leg by leg for each design load combination. The factored shear force, Vu of the leg, is determined and compared with the design shear strength ϕVn.

Design Strength

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

• ϕPn ≥ Pu

• ϕMn ≥ Mu

• ϕVn ≥ Vu

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

Strain, εt

Section Classification

ϕ

εtεty

Compression Controlled Moment

0.65

εty < εt < (εty + 0.003)

Transition region

0.65 + 0.25[(εt - εty)/0.003]

εt ≥ (εty + 0.003)

Compression Controlled Moment

0.90

Pn and Mn are calculated in accordance with Axial strength or Combined Flexural and Axial Strength per ACI 318-19 with ideCAD title.

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