Included code sections – 6.3.1(part), 6.3.2

Excluded code sections – 6.3.1(part), 6.3.3

Only the "core" of a cross section is used for torsion design. See "Concrete "Core" Determination".

If the core consists of multiple ribs, then the torsion calculations are performed for an average rib:

• 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.

Torsion truss properties are calculated in accordance with 6.3.2(1). Link dimensions are determined from the location of specified cover to longitudinal design bars and do not explicitly account for the location of user reinforcement. The truss wall thickness, t_ef,i is limited by:

• A/u per 6.3.2(1)
• b_w/2
• h/2
• horizontal spacing between outermost horizontal bars
• vertical spacing between outermost horizontal bars

The above limitations effectively create a truss wall with a longitudinal bar located at the center of the wall or outside the center of the wall (which is considered to be conservative). In these calculations RAM Concept assumes that the side cover to the longitudinal bars is the maximum of the top and bottom cover.

If the interaction equation 6.31 is satisfied, only minimum reinforcement is provided.

If equation 6.31 is not satisfied, equation 6.29 is used to calculate a maximum shear capacity by deducting the torsion portion of the interaction capacity. This equation is used to iteratively solve for the smallest value of theta that can satisfy the interaction equation 6.29. This theta is then used in all subsequent shear and torsion calculations.

Maximum spacing of links is calculated in accordance with 9.2.3(3).

Minimum torsion reinforcement is provided in accordance with 9.2.3(2).

Minimum longitudinal tension reinforcement is calculated in accordance with equation 6.28. The tension demand on a particular face is reduced by the minimum expected compression chord force.

If torsion design is selected and the torsion is greater than zero, at least minimum links will be provided.