How does ideCAD control beam reinforcement limits according to ACI 318-19?
Longitudinal and Transverse reinforcement limits are controlled automatically.
Acp = area enclosed by outside perimeter of concrete cross section, in.2
Al = total area of longitudinal reinforcement to resist torsion, in.2
Al,min = minimum area of longitudinal reinforcement to resist torsion, in.2
As = area of nonprestressed longitudinal tension reinforcement, in2
As,min = minimum area of flexural reinforcement, in.2
At = area of one leg of a closed stirrup, hoop, or tie resisting torsion within spacing s, in.2
Av = area of shear reinforcement within spacing s, in.2
Av,min = minimum area of shear reinforcement within spacing s, in.2
bw = web width or diameter of circular section, in.
d = distance from extreme compression fiber to centroid of longitudinal tension reinforcement, in.
fc' = specified compressive strength of concrete, psi
√fc‘ = square root of specified compressive strength of concrete, psi
fy = specified yield strength for nonprestressed reinforcement, psi
fyt = specified yield strength of transverse reinforcement, psi
h = overall thickness, height, or depth of member, in.
s = center-to-center spacing transverse reinforcement, in
Tcr = cracking torsional moment, in.-lb
Tth = threshold torsional moment, in.-lb
Tn = nominal torsional moment strength, in.-lb
Tu = factored torsional moment at section, in.-lb
Vc = nominal shear strength provided by concrete, lb
Vn = nominal shear strength, lb
Vs = nominal shear strength provided by shear reinforcement, lb
Vu = factored shear force at section, lb
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 = ratio of As to bd
Minimum flexural reinforcement
According to ACI 220.127.116.11, a minimum area of flexural reinforcement, As,min is equal to the greater of the following relations;
According to ACI 18.104.22.168, if As provided at every section is greater than one-third of As calculated by analysis, As,min need not be satisfied.
Minimum shear reinforcement
If shear reinforcement is required, minimum shear reinforcement area, Av,min, should be considered in accordance with ACI Table 22.214.171.124.
For nonprestressed beams, minimum shear reinforcement area, Av,min, should be provided in all sections where Vu >ϕλ √fc‘ bwd, except for the cases given in ACI Table 126.96.36.199. For the cases given in ACI Table 188.8.131.52., Av,min, should be provided where Vu>ϕVc
In other words, if ϕλ√fc‘(bwd) < Vu < [ Vc + 8√fc‘(bwd) ], the minimum shear reinforcement area, Av,min, is calculated given below.
Minimum torsional reinforcement
If Tu < ϕTth, torsional effects are ignored.
If ϕTcr > Tu ≥ ϕTth, only minimum torsional reinforcement needs to be provided given below;
Minimum transverse reinforcement (Av + 2At)min / s
the minimum area of longitudinal reinforcement Al,min
Reinforcement Limits for Beams of Earthquake-Resistant Structures
Ordinary moment frames
All the conditions and calculations described above are valid for beams of ordinary moment frames.
Intermediate moment frames
All the conditions and calculations described above are valid for beams of intermediate moment frames.
Special moment frames
All the conditions and calculations described above are valid for beams of special moment frames.
According to ACI 184.108.40.206; Longitudinal reinforcement should be satisfied the conditions given below;
Beams should have a minimum of two continuous bars at the top and bottom faces.
The reinforcement ratio ρ shall not exceed 0.025 for Grade 60 or S420 reinforcement and 0.02 for Grade 80 reinforcement.