## Scu

Fc c bw

(3) The concrete stress in the struts should be limited to Bc r vfcd where V is the effectiveness factor given by:

(4) The following detailing rules apply to the provision of shear reinforcement:

— the minimum percentage of shear reinforcement in 5.4.2.2.

— the limitation of the crack widths in the web in 4.4.2.

— the detailing arrangements for shear reinforcement in 5.4.2. 4.3.2.4.3 Standard method

(1) The shear resistance of a section with shear reinforcement is given by the equation:

Vcd is the contribution of the concrete and is equal to VRd1, calculated in accordance with 4.3.2.3 or as enhanced in 4.3.2.2(9). Vwd is the contribution of the shear reinforcement.

(2) The contribution of vertical shear reinforcement is given by the equation:

sw s

'wd " s • — - xyvd where Asw is the cross-sectional area of the shear reinforcement. s is the spacing of the stirrups.

fywd is the design yield strength of the shear reinforcement.

(3) The contribution of inclined shear reinforcement is given by the equation:

wd sw s

s is the spacing measured along the longitudinal axis, (see Figure 4.13).

(4) When checking against crushing at the compression struts, VRd2 is given by the equation:

For vertical stirrups, or for vertical stirrups combined with bent-up bars, cota is taken as zero.

(5) The forces in the tension chords of beams may be obtained from Equation (4.30) with cot 0 = |1| 4.3.2.4.4 Variable strut inclination method

(1) The notation used is given in Figure 4.13. The angle of the concrete struts 0 with the longitudinal axis is limited to:

for beams with constant longitudinal reinforcement; and to

for beams with curtailed longitudinal reinforcement. Other limiting values of 0 may be used provided they can be justified.

(2) For elements with vertical shear reinforcement, the shear resistances are defined by: VRd2 = bwz v fcd/(cot0 + tan0) As

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