Identification of Cracks

1a-

Observation -

• Concrete crushed and the reinforcement exposed.
• Concrete spalled beyond the reinforcement which may be sign of rupture.
• Beam top portion looks safe because of the flange advantage from slab.
• The crack develops from the bottom to top means rebar yielding occurs in support bottom only.

Answer -

• it's form of flexural failure due to reversal of stress during earthquake.
• During stress reversal , support top experiences compression and bottom experiences tension.
• Top compression is managed by slab advantage. Bottom tension was not satisfied by the provided reinforcement.
• Since the reinforcement got yielded, it can not be repaired.

1b - observation -

• Crack along beam column edge.
• Cracks seem to have developed through the structure as it looks much wider.
• Beam looks separated from column at joints .
• Concrete is not severely crushed.

Answer -

• It's beam pull out failure due to insufficient development length of reinforcement in joint.
• During earthquake, the horizontal movement of structure makes this condition worse and detached the beam member from column.
• Providing anchorage length between two existing concrete is very difficult. So not repairable

1c -

observation -

• Crack are exactly at the joint of the column beam .
• Cracks in beam developed through its entire width.
• Slab also developed more cracks along the beam width direction.

Answer -

• It's a plastic hinge failure.
• The damage occurred only in the joint zone first of all .
• Cyclic lateral loading and stress reversal at the joints led to the damage.
• Even the slab participated to its best to handle the tension( slab is severely cracked means has undergone tension with its flange conditions. )but unable to control the damage.
• The joint can be strengthened.

2a -Observation

• concrete damaged at top of a column.
• concrete damaged all around the column face.
• beam are safe .
• The location of column looks at edge of the building.
• no walls are built along the column means it is probably at ground floor , for parking car movement access.

Answer-

• its a soft failure, technically plastic hinge formation.
• due to the absence of infill walls at the ground floor, the plastic hinge forms at the top of ground story columnss during lateral movement.
• based on the development of crush concrete, it can either be repairable or non repairable.

2b - observation

• concrete developed complete breakage diagonally
• longitudinal reinforcements are intact.
• shear reinforcement spacing looks wider(which means probably lesser shear rebar provided).

Answer

• its a pure shear failure.
• inadequate shear reinforcement compels concrete takes all the shear stresses.

2c - Observation

• column failed completely.
• failure at top of column.
• there are two slabs connected to the column, probably one at mid height of the column.
• the wooden piles might be a post failure support after column failed, providing temporary prop to avoid thecollaps of the entire structure.