Section 22.5 Torsion
Included code sections - 22.5.1, 22.5.3.1, 22.5.3.2, 22.5.4, 22.5.5 (item a and b)
Excluded code sections - 22.5.2, 22.5.3.3, 22.5.5 (item c and d)
Only the core of a cross section is used for torsion design. See Concrete Core Determination .
- rib width = total core width / num ribs
- with ultimate forces scaled down by the number of ribs (/ num ribs) and capacity and reinforcement scaled back up by the number of ribs (* num ribs).
- code provisions are not applicable to multiple ribs, so to get a more exact calculation, use a separate design section or design strip for each rib.
Equivalent bending moment Me1 and Me2 are calculated per sections 22.5.3.1 and 22.5.3.2.
Transverse bending moment Me3 is calculated and reported in the auditor per 22.5.3.3, but no transverse bending design is performed.
Shear and torsion reinforcement is provided in accordance with sections 22.5.4.1, 22.5.4.2, 22.5.4.3 and 22.5.4.4. In the shear equation for Av in section 22.5.4.3, " dt " is substituted for " dl " to align this equation with the shear equation in 22.4.3.2 when no torsion is present. This change may not be conservative, but is consistent with the publication mentioned in the note below.
Distribution of torsion reinforcement is calculated in accordance with section 22.5.5.
Maximum spacing of torsion stirrups is the least of x1, (x1 + y1)/4 or 200 mm.
If torsion design is selected, at least minimum stirrups will be provided at all locations.