Section 22.4 Design shear resistance of beams

V_co is calculated per section 22.4.1. The flange/web intersection is not checked.

V_cr is calculated per section 22.4.2.

The value of V_c is used as shown in the following table.

Table 1. V_c rule mapping
Moment	Vc Implementation
M < M_o	V_c = V_co V_c= (stress)bh
M ≥ M_o and tension is on the "tension" face *	V_c = min (V_co, V_cr) V_c = (stress)bh
M ≥ M_o and no tension on the "tension" face *	V_c = min (V_co, V_cr) V_c = (stress)bh d = d_t (assumed) A_s = 0 (none in "tension zone") A_ps = 0 (none in "tension zone")

Note: * The calculation of M_o uses only 80% of the stress due to prestress. This can produce the rare case where the section is in reality uncracked and has a tension face different to that calculated with M_o. For the unusual case of M ≥ M_o and the section is actually uncracked (when considering the full prestress force) the conservative assumptions of column four are made.

"d" is defined as the depth to the centroid of the tension force in the tension zone (including rebar and post-tensioning). This is slightly different (and likely more rational) than the distance from the extreme compression fibre to the centroid of the tendons as defined in the code.

" d_t " is defined as the maximum depth to any longitudinal mild reinforcement, or the depth to the centroid of the tendons, whichever is greater.

The vertical tendon force component is ignored.

For sections with multiple concrete mixes, the minimum f_cu is used in calculations.

Longitudinal reinforcement designed by Minimum, Service and Strength designers is considered in the determination of A_p used in the calculation of v_c.

b is adjusted by considering any tendons in the shear core. The full width of unbonded tendons is deducted, and two-thirds of the width of bonded tendons is deducted from b.

For cross sections with multiple tendons, the f_pu and f_pe values used in the calculations are averaged.

Longitudinal unstressed reinforcement is converted into equivalent area of prestressed reinforcement to determine A_p used in Table 6.

When calculating f_pe/f_pu, f_pe is taken as the effective prestressing force divided by the equivalent area of prestressing steel.

v_c is calculated per the equation in SP : 24 - 1983 to calculate values from Table 6.

For slabs, Table 6 values are modified by IS 456 40.2.1.1 as appropriate.

Maximum shear stress is in accordance with Table 7. For slabs, this value is adjusted in accordance with IS 456 40.2.3.1.

Shear reinforcement is calculated per 22.4.3.

Minimum shear reinforcement is provided at all locations in beams.

Minimum reinforcement is provided in slabs when V_u > V_c.

The "web thickness" used in the calculations is the same as the shear core width - this may be incorrect if the core width is made up of multiple webs. In such cases, multiple design sections or design strips can be used; each containing only one web.