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# 22.7 Torsional Strength

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This section shall apply to members if

**, where***T*≥ ϕ_{u}*T*_{th}**ϕ**is given in Chapter 21 and threshold torsion**is given in 22.7.4. If***T*_{th}**, it shall be permitted to neglect torsional effects.***T*< ϕ_{u}*T*_{th}Nominal torsional strength shall be calculated in accordance with 22.7.6.

The value of used to calculate

**and***T*_{th}**shall not exceed 100 psi.***T*_{cr}The values of

**and***f*_{y}**for longitudinal and transverse torsional reinforcement shall not exceed the limits in 20.2.2.4.***f*_{yt}If

**and***T*≥ ϕ_{u}*T*_{cr}**is required to maintain equilibrium, the member shall be designed to resist***T*_{u}**.***T*_{u}In a statically indeterminate structure where

**and a reduction of***T*≥ ϕ_{u}*T*_{cr}**can occur due to redistribution of internal forces after torsional cracking, it shall be permitted to reduce***T*_{u}**to***T*_{u}**ϕ**, where the cracking torsion*T*_{cr}**is calculated in accordance with 22.7.5.***T*_{cr}If

**is redistributed in accordance with 22.7.3.2, the factored moments and shears used for design of the adjoining members shall be in equilibrium with the reduced torsion.***T*_{u}Threshold torsion

**shall be calculated in accordance with Table 22.7.4.1(a) for solid cross sections and Table 22.7.4.1(b) for hollow cross sections, where***T*_{th}**is positive for compression and negative for tension.***N*_{u}**Table 22.7.4.1(a)—Threshold torsion for solid cross sections**

Type of member | T_{th} | |
---|---|---|

Nonprestressed member | (a) | |

Prestressed member | (b) | |

Nonprestressed member subjected to axial force | (c) |

**Table 22.7.4.1(b)—Threshold torsion for hollow cross sections**

Type of member | T_{th} | |
---|---|---|

Nonprestressed member | (a) | |

Prestressed member | (b) | |

Nonprestressed member subjected to axial force | (c) |

Cracking torsion

**shall be calculated in accordance with Table 22.7.5.1 for solid and hollow cross sections, where***T*_{cr}**is positive for compression and negative for tension.***N*_{u}**Table 22.7.5.1—Cracking torsion**

Type of member | T_{cr} | |
---|---|---|

Nonprestressed member | (a) | |

Prestressed member | (b) | |

Nonprestressed member subjected to axial force | (c) |

For nonprestressed and prestressed members,

**shall be the lesser of (a) and (b):***T*_{n}(a) | (22.7.6.1a) | |

(b) | (22.7.6.1b) |

where ** A_{o}** shall be determined by analysis,

**θ**shall not be taken less than 30 degrees nor greater than 60 degrees;

**is the area of one leg of a closed stirrup resisting torsion;**

*A*_{t}**is the area of longitudinal torsional reinforcement; and**

*A*_{ℓ}**is the perimeter of the centerline of the outermost closed stirrup.**

*p*_{h}Cross-sectional dimensions shall be selected such that (a) or (b) is satisfied:

(a) For solid sections

(22.7.7.1a) |

(b) For hollow sections

(22.7.7.1b) |

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