Two-Way Shear Capacity

Two-way shear, or punching shear, is taken for a section that is a distance of 1.5d (BS8110: Part 1, Section 3.7.7.6) from the edge of the concrete column (or modified base plate dimensions). It is also checked at the column face to be the lesser of

{\begin{matrix} 0.8 \sqrt{f_{c u}} \\ and \\ 5 {N/mm}^{2} \end{matrix}} b_{o} d

The shear capacity is calculated using the same equation in BS8110: Part 1, Table 3.8, Note 2 with b substituted for b_o - the perimeter length of the critical section.

Two-Way Shear Critical Section

The ultimate applied shear V_u on the critical section is calculated as:

V_{u} = (\begin{matrix} P(Column Load) + \\ Self Weight of Critical Section + \\ Factored Surcharge on Critical Section + \\ Soil Stress Under Critical Section \end{matrix})

Equation 5-2

Note: A two-way shear check is done assuming an "interior" column that is far from any slab edges. If the supported column is close enough to the footing edge or corner, the user will need to do supplemental checks to confirm that the footing capacity is acceptable.