Explain the diaphragm and connection failure in detail

Diaphragm failure is a rare phenomenon in the event of seismic motion. Damage to the diaphragm never impairs its gravity load carrying capacity. Lack of motion anchoring produces a non-bending cantilever action at the base of the wall resulting from the push of the diaphragm against the wall.

The absence of a good shear transfer between the diaphragms, reaction walls, and,  in-plane rotation of the diaphragms ends to account for the damage which takes place at the corners of the wall. The problem remains non-existent in strengthened buildings and is very rare in anchored buildings. In strengthened buildings, separation remains worse at or near the centreline of the diaphragm.

In connection failure, the lack of bond beams, poor connections among the walls and the roofs, and large unsupported wall lengths cause the separation of walls and cause damage to occur via the out-of-plane mechanism. Thus, the whole or the significant parts of the wall fall during the earthquake.