Vertical Shear

Eurocode 2 introduces the strut inclination method for shear capacity checks. In this method the shear is resisted by concrete struts acting in compression and shear reinforcement acting in tension.

The angle of the concrete strut varies, depending on the shear force applied (see figure below).

Strut inclination method

The procedure for determining the shear capacity of a section is shown in the accompanying flow chart (which includes UK NA values) and is in terms of shear stress in the vertical plane rather than a vertical force as given in Eurocode 2.

Where shear reinforcement is required, then the angle of the concrete strut should be calculated. For many typical beams the minimum angle of strut will apply (when cot theta = 2.5 or theta =21.8º) i.e. for class C30/37 concrete the strut angle exceeds 21.8º only when the shear stress is greater than 3.27 N/mm² (refer to Table 7).

As with BS 8110, there is a maximum permitted shear capacity, v_Rd,_{max ,} (when cot theta = 1.0 or theta = 45º), but this is not restricted to 5 MPa as in BS 8110.