B-6Torsion

IS 456:2000, Plain and Reinforced Concrete — Code of Practice

Last Updated 29 Oct 2026

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B-6.1 General

In structures where torsion is required to maintain

equilibrium, members shall be designed for torsion in accordance with B-6.2, B-6.3 and B-6.4. However, for such indeterminate structures where torsion can be eliminated by releasing redundant restraints, no specific design for torsion is necessary provided torsional stiffness is neglected in the calculation of internal forces. Adequate control of any torsional cracking is provided by the shear reinforcement as per B-5.

NOTE — The approach to design in this clause for torsion is as follows:

Torsional reinforcement is not calculated separately from

reinforcement is not calculated separately from that required for bending and shear. Instead the total longitudinal reinforcement is determined for a fictitious bending moment which is a function of actual bending moment and torsion; similarly web reinforcement is determined for a fictitious shear which is a function of actual shear and torsion.

B-6.1.1

The design rules laid down in B-6.3 and B-6.4 shall apply to beams of solid rectangular cross-section. However, these clauses may also be applied to flanged beams by substituting $b_{w}$ for $b$ , in which case they are generally conservative; therefore specialist literature may be referred to.

B-6.2 Critical Section

Sections located less than a distance $d$ , from the face of the support may be designed for the same torsion as computed at a distance $d$ , where $d$ is the effective depth.

B-6.3 Shear and Torsion

B-6.3.1 Equivalent Shear

Equivalent shear, $V_{\mathrm{e}}$ shall be calculated from the formula:

$V_{\mathrm{e}}=V+1.6$ where

$V_{e}=$ equivalent shear,

$V=\operatorname{shear}$ ,

$\begin{aligned} V & =\text { shear, } \\ T & =\text { torsional moment, and }\end{aligned}$

$b \quad=$ breadth of beam.

The equivalent nominal shear stress, $\tau_{v c}$ , in this case shall be calculated as given in B-5.1, except for substituting $V$ by $V_{e}$ . The values of $\tau_{v c}$ shall not exceed the values of $\tau_{c \max }$ given in Table 24.

B-6.3.2

If the equivalent nominal shear stress $\tau_{v e}$ does not exceed $\tau_{v}$ , given in Table 23, minimum shear reinforcement shall be provided as specified in 26.5.1.6.

B-6.3.3

If $\tau_{v c}$ exceeds $\tau_{c}$ given in Table 23, both longitudinal and transverse reinforcement shall be provided in accordance with B-6.4.

B-6.4 Reinforcement in Members Subjected to Torsion

B-6.4.1

Reinforcement for torsion, when required, shall consist of longitudinal and transverse reinforcement.

B-6.4.2 Longitudinal Reinforcement

The longitudinal reinforcement shall be designed to

resist an equivalent bending moment, $M_{\mathrm{e} 1}$ , given by

$M_{\mathrm{cl}}=M+M_{\mathrm{l}}$

where

$M=$ bending moment at the cross-section, and

$M_{\mathrm{t}}=T \frac{(1+D / b)}{1.7}$ , where $T$ is the torsional moment, $D$ is the overall depth of the beam and $b$ is the breadth of the beam.

B-6.4.2.1

If the numerical value of $M_{\mathrm{i}}$ as defined in B-6.4.2 exceeds the numerical value of the moment $M$ , longitudinal reinforcement shall be provided on the flexural compression face, such that the beam can also withstand an equivalent moment $M_{\mathrm{e} 2}$ given by $M_{\mathrm{e} 2}=M_{\mathrm{i}}-M$ , the moment $M_{\mathrm{e} 2}$ being taken as acting in the opposite sense to the moment $M$ .

B-6.4.3 Transverse Reinforcement

Two legged closed hoops enclosing the corner longitudinal bars shall have an area of cross-section $A_{\mathrm{sv}}$ , given by

$A_{\mathrm{sv}}=\frac{T . s_{\mathrm{y}}}{b_{1} d_{1} \sigma_{\mathrm{sv}}}+\frac{V . s_{\mathrm{y}}}{2.5 d_{1} \sigma_{\mathrm{sv}}}$ , but the total

transverse reinforcement shall not be less than

$\frac{\left(\tau_{\mathrm{ve}}-\tau_{\mathrm{c}}\right) b . s_{\mathrm{v}}}{\sigma_{\mathrm{sv}}}$

where

$T=$

torsional moment.

$\begin{aligned} T & =\text { torsional mo } \\ V & =\text { shear force, }\end{aligned}$

$s_{\mathrm{v}}=$ spacing of the stirrup reinforcement,
$\begin{aligned} b_{1} & =\text { centre-to-centre distance between corner } \\ & \text { bars in the direction of the width, }\end{aligned}$
$\begin{aligned} d_{\mathrm{i}} & =\text { centre-to-centre distance between corner } \\ & \text { bars in the direction of the depth, }\end{aligned}$
$b \quad=$ breadth of the member,
$\sigma_{\mathrm{v}}=$ permissible tensile stress in shear reinforcement,
$\tau_{w}=$ equivalent shear stress as specified in B-6.3.1, and
$\begin{aligned} \tau_{\mathrm{c}} & =\text { shear strength of the concrete as specified } \\ & \text { in Table 23. }\end{aligned}$

End of chapter · NextAnnex C (Clauses 22.3.2, 23.2.1 and 42.1) calculation of deflection

B-6Torsion

IS 456:2000, Plain and Reinforced Concrete — Code of Practice

Last Updated 29 Oct 2026

Hover any section to copy its link or text, ask Copilot about it, or bookmark it.

B-6.1 General

In structures where torsion is required to maintain

NOTE — The approach to design in this clause for torsion is as follows:

Torsional reinforcement is not calculated separately from

B-6.1.1

B-6.2 Critical Section

Sections located less than a distance $d$ , from the face of the support may be designed for the same torsion as computed at a distance $d$ , where $d$ is the effective depth.

B-6.3 Shear and Torsion

B-6.3.1 Equivalent Shear

Equivalent shear, $V_{\mathrm{e}}$ shall be calculated from the formula:

$V_{\mathrm{e}}=V+1.6$ where

$V_{e}=$ equivalent shear,

$V=\operatorname{shear}$ ,

$\begin{aligned} V & =\text { shear, } \\ T & =\text { torsional moment, and }\end{aligned}$

$b \quad=$ breadth of beam.

B-6.3.2

If the equivalent nominal shear stress $\tau_{v e}$ does not exceed $\tau_{v}$ , given in Table 23, minimum shear reinforcement shall be provided as specified in 26.5.1.6.

B-6.3.3

If $\tau_{v c}$ exceeds $\tau_{c}$ given in Table 23, both longitudinal and transverse reinforcement shall be provided in accordance with B-6.4.

B-6.4 Reinforcement in Members Subjected to Torsion

B-6.4.1

Reinforcement for torsion, when required, shall consist of longitudinal and transverse reinforcement.

B-6.4.2 Longitudinal Reinforcement

The longitudinal reinforcement shall be designed to

resist an equivalent bending moment, $M_{\mathrm{e} 1}$ , given by

$M_{\mathrm{cl}}=M+M_{\mathrm{l}}$

where

$M=$ bending moment at the cross-section, and

$M_{\mathrm{t}}=T \frac{(1+D / b)}{1.7}$ , where $T$ is the torsional moment, $D$ is the overall depth of the beam and $b$ is the breadth of the beam.

B-6.4.2.1

B-6.4.3 Transverse Reinforcement

Two legged closed hoops enclosing the corner longitudinal bars shall have an area of cross-section $A_{\mathrm{sv}}$ , given by

$A_{\mathrm{sv}}=\frac{T . s_{\mathrm{y}}}{b_{1} d_{1} \sigma_{\mathrm{sv}}}+\frac{V . s_{\mathrm{y}}}{2.5 d_{1} \sigma_{\mathrm{sv}}}$ , but the total

transverse reinforcement shall not be less than

$\frac{\left(\tau_{\mathrm{ve}}-\tau_{\mathrm{c}}\right) b . s_{\mathrm{v}}}{\sigma_{\mathrm{sv}}}$

where

$T=$

torsional moment.

$\begin{aligned} T & =\text { torsional mo } \\ V & =\text { shear force, }\end{aligned}$

$s_{\mathrm{v}}=$ spacing of the stirrup reinforcement,
$\begin{aligned} b_{1} & =\text { centre-to-centre distance between corner } \\ & \text { bars in the direction of the width, }\end{aligned}$
$\begin{aligned} d_{\mathrm{i}} & =\text { centre-to-centre distance between corner } \\ & \text { bars in the direction of the depth, }\end{aligned}$
$b \quad=$ breadth of the member,
$\sigma_{\mathrm{v}}=$ permissible tensile stress in shear reinforcement,
$\tau_{w}=$ equivalent shear stress as specified in B-6.3.1, and
$\begin{aligned} \tau_{\mathrm{c}} & =\text { shear strength of the concrete as specified } \\ & \text { in Table 23. }\end{aligned}$

End of chapter · NextAnnex C (Clauses 22.3.2, 23.2.1 and 42.1) calculation of deflection