What does DIAPH stand for?

Diaphragm

A diaphragm is something flexible that muscular wall that can be stretchable across the body for making suction and pressure other side. Roof panel or decking, metal wall, or floor slab which provides a larger in-plane shear stiffness and strength adequate to transmit horizontal forces to the resisting structural system. A plate or partition between opposite parts of a member, serving a definite purpose in the structural design of the member.