Where a thin composite slab has to be designed to resist point lads (e.g. from a steel wheel of a loaded trolley), resistance to punching shear may be critical. Failure is assumed to occur on a critical perimeter, of length Cp, which is defined as for reinforced concrete slabs. For a loaded area ap by bp, remote from a free edge, and 45°spread through a screed of thickness hf, it is as shown in Fig.3.5(a):
where hc is the thickness of the slab above the sheeting. Small ribs of the type shown in Fig.3.5(b)
can be neglected when hc is determined.
