Beam Section Torsion Capacity

Torsional reinforcement is not required when:

T_{U} < ϕ \sqrt{{f^{'}}_{c}} (\frac{A_{c p}^{2}}{p_{c p}}) = ϕ_{T} T_{c}

ACI 11.6.1

where

A_cp	=	hb
p_cp	=	2(h+b_w)

Note: The beam section is considered to be rectangular for the calculation of the torsional moment of inertia (torsional constant) J, A_cp, and p_cp regardless of the flange width and thickness. This reduces J which reduces the likelihood of the beam requiring torsion reinforcement.

When T_u is found to be larger than the above limit at any location along the span at least a distance d from each support (per ACI 11.6.2.4), a warning will be generated.