Prescriptive breakaway walls are code compliant, with resistance between 10 and 20 psf. If the breakaway resistance exceeds 20 psf, then an engineer must certify that the wall will fail under base load loads with no damage to the structure.
Frangible building elements are ones that are designed to break into small pieces that will not cause an obstruction to flow or damage other structures. Examples of frangible elements include breakaway walls as well as small non-structural slabs with saw-cut joints beneath elevated coastal buildings.