Shear Wall Reinforcement Limits per ACI 318-19 with ideCAD

How does ideCAD control shear wall reinforcement limits according to ACI 318-19?

• Longitudinal and Transverse reinforcement limits are controlled automatically.

Notation

A_cv = gross area of concrete section bounded by web thickness and length of section in the direction of shear force considered in the case of walls, and gross area of concrete section in the case of diaphrams. Gross area is total area of defined section minus area of any openings, in.²
f_c^' = specified compressive strength of concrete, psi
√f_c‘ = square root of specified compressive strength of concrete, psi
f_y = specified yield strength for nonprestressed reinforcement, psi
f_yt = specified yield strength of transverse reinforcement, psi
h_w = height of entire wall from base to top, or clear height of wall segment or wall pier considered, in.
l_w = length of entire wall, or length of wall segment or wall pier considered in direction of shear force, in.
M_u = factored moment at section, in.-lb
V_n = nominal shear strength, lb
V_u = factored shear force at section, lb
α_c = coefficient defining the relative contribution of concrete strength to nominal wall shear strength
ϕ = strength reduction factor
λ = modification factor to reflect the reduced mechanical properties of lightweight concrete relative to normalweight concrete of the same compressive strength
ρ_l = ratio of area of distributed longitudinal reinforcement to gross concrete area perpendicular to that reinforcement
ρ_t = ratio of area of distributed transverse reinforcement to gross concrete area perpendicular to that reinforcement

According to ACI 11.6.1, minimum values of reinforcement ratios are given below.

The minimum value of distributed longitudinal reinforcement ratio ρ_l is 0.0025

The minimum value of distributed transverse reinforcement ratio ρ_t is 0.0025

Earthquake Resistant Structures

Special structural walls

According to ACI 18.10.2.1, the minimum value of distributed longitudinal reinforcement ratio, ρ_l, and distributed transverse reinforcement ratio, ρ_t, should be 0.0025, except that if V_u < λ√f_c‘A_{cv ,} ρ_t can be reduced to the values in ACI 11.6 explained above. Maximum reinforcement spacing in each direction in structural walls is 18 inches.

According to ACI 18.10.2.2, if V_u > 2λ√f_c‘A_cv or h_w/l_w ≥ 2.0, at least two curtains of reinforcement should be used in a shear wall.

According to ACI 18.10.2.4, walls or wall piers with h_w/l_w ≥ 2.0 that are effectively continuous from the base of the structure to the top of the wall and are designed to have a single critical section for flexure and axial loads should have longitudinal reinforcement at the ends of a vertical wall segment that satisfies conditions given below;

• minimum longitudinal reinforcement ratio in area 0.15l_w from the end of a vertical wall segment and over a width equal to the wall thickness should be 6√f_c‘/f_y.

• Longitudinal reinforcement should extend vertically above and below the critical section at least the greater of l_w and M_u/3V_u.

• No more than 50 percent of the longitudinal reinforcement should be terminated at any one section.

According to ACI 18.10.4.3, shear walls should have distributed shear reinforcement in two orthogonal directions in the plane of the wall. If h_w/l_w ≤ 2.0, the reinforcement ratio ρ_l should be at least the reinforcement ratio ρ_t.

Next Topic

Shear Wall Reinforcement Detailing per ACI 318-19 with ideCAD

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