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.
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Notation
A_{g }= gross area of concrete section, in^{2}
A_{v }= area of shear reinforcement within spacing s, in.^{2}
D = dead load
E _{ } = earthquake load
f_{c}^{'}_{ }= specified compressive strength of concrete, psi
f_{yt }= specified yield strength of transverse reinforcement, psi
L _{ } = live load
L_{r} _{ } = roof live load
M_{n }= nominal flexural strength at section, in.-lb
M_{u}_{ } = factored moment at section, in.-lb
P_{n}_{ } = nominal axial compressive strength of member, lb
P_{u}_{ } = factored axial force; to be taken as positive for compression and negative for tension, lb
R _{ } = rain load
S _{ } = snow load
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
V_{n }= nominal shear strength, lb
V_{u }= factored shear force at section, lb
W_{ } = wind load
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 (M_{u}, P_{u}) 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, V_{u} of the leg, is determined and compared with the design shear strength ϕV_{n.}
Design Strength
Design strength in all sections should satisfy all conditions given below;
ϕP_{n} ≥ P_{u}
ϕM_{n} ≥ M_{u}
ϕV_{n} ≥ V_{u}
Strength reduction factors ϕ is determined according to using ACI Table 21.2.2. Interaction between load effects is considered.
Strain, ε_{t} | Section Classification | ϕ |
---|---|---|
ε_{t} ≤ ε_{ty} | Compression Controlled Moment | 0.65 |
ε_{ty} < ε_{t} < (ε_{ty} + 0.003) | Transition region | 0.65 + 0.25[(ε_{t} - ε_{ty})/0.003] |
ε_{t} ≥ (ε_{ty} + 0.003) | Compression Controlled Moment | 0.90 |
P_{n} and M_{n} are calculated in accordance with Axial strength or Combined Flexural and Axial Strength per ACI 318-19 with ideCAD title.
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