Longitudinal reinforcement detailing is applied automatically in accordance with ACI 10.7.
Longitudinal reinforcement detailing is applied according to ACI Chapter 18 in earthquake resistant structure columns.
Notation
Ab = area of an individual bar or wire, in.2
fy = specified yield strength of nonprestressed reinforcement, psi
h = overall thickness, height, or depth of member, in.
ld = development length in tension of deformed bar, deformed wire, plain and deformed welded wire reinforcement, or pretensioned strand, in.
lu = 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 within rectangular or circular ties
Six enclosed by spirals or for columns of special moment frames enclosed by circular hoops
According to ACI 10.7.4.1, the slope of the bend part of an offset bent longitudinal bar relative to the longitudinal axis of the column should not exceed 1 in 6. Bend parts of bar above and below an offset should be parallel to 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 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 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, 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.
Minimum the lap splice length is 12 in.
If the reinforcement bar is tesile due to factored loads, tension lap splices should be permitted described in the Splices 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 Reistant Structures
Ordinary moment frames
All the longitudinal reinforment detailing conditions described above are applied to columns of ordinary moment frames.
Columns of Earthquake Reistant Structures
Intermediate moment frames
All the longitudinal reinforment detailing conditions described above are applied to columns of intermediate moment frames.
Columns of Earthquake Reistant Structures
Special moment frames
All the longitudinal reinforment detailing conditions described above are applied to columns of special moment frames.
The minimum number of longitudinal reinforcement for columns with cicular hoops, is six.
Longitudinal reinforcement is be selected as 1.25ld ≤ lu/2, over the column net height.