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Longitudinal Reinforcement (SwRD) per ACI 318-19 with ideCAD

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

  • Longitudinal reinforcement detailing is applied automatically in accordance with ACI 11.7

  • Longitudinal reinforcement detailing is applied according to ACI Chapter 18 in special structural walls.


Ag = gross area of concrete section, in2
Ast = total area of nonprestressed longitudinal reinforcement, in2
bw = web width or diameter of circular section, in.
d = distance from extreme compression fiber to centroid of longitudinal tension reinforcement, in.
db = nominal diameter of bar, wire, or prestressing strand, in
√fc = square root of specified compressive strength of concrete, psi
fy = specified yield strength of nonprestressed reinforcement, psi
fyt = specified yield strength of transverse reinforcement, psi
h = overall thickness, height, or depth of member, in.
hsx = story height for story x, in.
hw = height of entire wall from base to top, or clear height of wall segment or wall pier considered, in.
ld = development length in tension of deformed bar, deformed wire, plain and deformed welded wire reinforcement, or pretensioned strand, in.
lw = length of entire wall, or length of wall segment or wall pier considered in direction of shear force, in.
Mu = factored moment at section, in.-lb
s = center-to-center spacing of items, such as longitudinal reinforcement, transverse reinforcement, tendons, or anchors, in.
Vu = factored shear force at section, lb
ϕ = strength reduction factor

According to ACI, the maximum spacing of longitudinal reinforcement bars in shear walls is the lesser of 3h and 18 inches. If shear reinforcement is required for in-plane strength, maximum longitudinal reinforcement spacing is lw/3.

According to ACI, longitudinal reinforcement should be laterally supported by transverse reinforcement if the following two conditions are satisfied;

  • Ast > 0.01Ag

  • longitudinal reinforcement is required

Earthquake-Resistant Structures

Special structural walls

According to ACI, longitudinal reinforcement in structural walls should be satisfied the requirements in titles Development of Reinforcement per ACI 318-19 with ideCAD and Splices per ACI 318-19 with ideCAD as well as the following conditions;

  • Except at the top of a wall, longitudinal reinforcement shall extend at least 12 ft above the point at which it is no longer required to resist flexure but need not extend more than ld above the next floor level.

  • At locations where longitudinal reinforcement yielding is likely to occur due to lateral displacements, development lengths of longitudinal reinforcement should be 1.25 times the values calculated for fy in tension.

  • At locations where yielding of longitudinal reinforcement is likely to occur due to lateral displacements, lap splices of longitudinal reinforcement within boundary regions should not be permitted over a height equal to hsx above and ld below. The maximum value of hsx is 20 ft.

According to ACI, walls or wall piers with hw/lw ≥ 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 0.15lw from the end of a vertical wall segment and over a width equal to the wall thickness should be 6√fc‘/fy.

  • Longitudinal reinforcement should extend vertically above and below the critical section at least the greater of lw and Mu/3Vu.

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

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