S

hf,t

(minimum value when hw = 70bw)

(maximum value when hw = 35bw)

(a) Web depth taken for shear stress calculation when hw < 35bv (assuming a uniform shear stress profile)

(b) Web depth varies for shear stress calculation when 35bw < hw < 70bw (assuming a uniform shear stress profile)

Fig. 7.4. EC5 web strength criteria.

Although the shear stress in the web will vary, when hw < 35bw, assuming a uniform shear stress distribution, the depth of the web taken to be effective in resisting shear is (hw + 0.5(hfjt + hf>c)), as shown in Figure 7.4a. However, within the range 35bw < hw < 70bw the shear resistance is reduced due to buckling instability effects and, for an I (or box) section in this range, again assuming a uniform shear stress distribution, the depth of the web will be dependent on the value of hw as shown in Figure 7.4b.

The design requirements of EC5 are:

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