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

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

Notation

A_b = area of an individual bar or wire, in.²
f_y = specified yield strength of nonprestressed reinforcement, psi
h = overall thickness, height, or depth of member, in.
l_d = development length in tension of deformed bar, deformed wire, plain and deformed welded wire reinforcement, or pretensioned strand, in.
l_u = unsupported length of column or wall, in.
s = center-to-center spacing of items, such as longitudinal reinforcement, transverse reinforcement, tendons, or anchors, in.

For nonprestressed columns and for prestressed columns, the minimum number of longitudinal bars should be three conditions given below,

• Three within triangular ties

• Four rectangular or circular ties

• Six enclosed by spirals or columns of special moment frames enclosed by circular hoops

According to ACI 10.7.4.1, the slope of the bent part of an offset bent longitudinal bar relative to the longitudinal axis of the column should not exceed 1 in 6. Bend parts of the bar above and below an offset should be parallel to the column axis.

According to ACI 10.7.4.2, Longitudinal bars shall not be offset bent if the column face is offset 3 in. or more. Also, separate dowels, lap spliced with the longitudinal bars adjacent to the offset column faces, should be provided.

Lap splices of deformed reinforcement are applied according to the conditions given in Splices per ACI 318-19 with ideCAD title. Clear spacing of longitudinal reinforcement should be considered, as shown in the picture below.

Lap splices vary depending on the compression or tension of the reinforcement. If the reinforcement bar is compressive due to factored loads, compression lap splices should be permitted described in the Splices per ACI 318-19 with ideCAD title. Lap splice length can be decreased in accordance with two conditions below;

• For tied columns, if ties throughout the lap splice length have an effective area not less than 0.0015hs in both directions, the lap splice length can be reduced by multiplying 0.83. Tie legs perpendicular to dimension h is considered in calculating effective area.

• For spiral columns, if spirals throughout the lap splice length satisfy conditions given in ACI 25.7.3, lap splice length can be reduced by multiplying 0.75.

The minimum lap splice length is 12 in.

If the reinforcement bar is tensile due to factored loads, tension lap splices should be permitted described in the Splices per ACI 318-19 with ideCAD title. Also, the conditions given in ACI Table 10.7.5.2.2 should be provided.

Details for end-bearing splices are provided in ACI 25.5.6.

Columns of Earthquake-Resistant Structures

Ordinary moment frames

All the longitudinal reinforcement detailing conditions described above are applied to columns of ordinary moment frames.

Columns of Earthquake-Resistant Structures

Intermediate moment frames

All the longitudinal reinforcement detailing conditions described above are applied to columns of intermediate moment frames.

Columns of Earthquake-Resistant Structures

Special moment frames

All the longitudinal reinforcement detailing conditions described above are applied to columns of special moment frames.

The minimum number of longitudinal reinforcements for columns with circular hoops is six.

Longitudinal reinforcement is selected as 1.25l_d ≤ l_u/2, over the column net height.