Why do engineer chamfer or fillet sharp edges?
The reason is that as the material design comes to a sharp edge there is lesser and lesser material,
So at these edges the material is weaker and weaker thus subject to uncontrolled breakage or chipping.
to avoid this in concrete, engineers design in a chamfer usually at small 45degree angle that is added to the formwork.
For metals, like steel, engineers round off the corners specifying in the design a fillet or rounding of edges where possible to eliminate any pressure or stress points that weaken the metal.
As an aside, Architects love "clean" sharp edges, which puts structural engineers in direct conflict with these designs.
