Large support reactions (or any load) applied over a small area of a slab can cause the slab to fail near the perimeter of the support in shear-like failure. This "punching shear" is different from "beam shear" because the failure location is around a perimeter instead of along a line across the slab. Bending moment reactions applied along with the reaction force tend to lower the amount of load that can be supported without a punching failure. Local thickenings of a slab may increase the punching shear resistance, or may just move the punching shear failure location to a perimeter outside of the thickened area. Punching shear failures are usually brittle and sudden.