Identification of Cracks

ANS - 1(A)

Observations:

• concrete crushed and the reinforcement is exposed.
• concrete spalled beyond the reinforcement which may be a sign of rupture.
• The crack develops fro bottom to top means rebar yielding occurs in support bottom only.

CAUSE OF FAILURE:

• Its form of flexural failure due to reversal of stress during earthquake.
• During stress reversaal support top experiences compression and bottom experiences tension.
• Since the reinforcement got yielded , it can not be repaired.
  

ANS - 1(B)

Observations:

• Cracks along beam - column edge.
• Beams looks separated from the column at joints.
• Concrete is not severely crushed.

CAUSE OF FAILURE:

• Its Beam pull out failure due to insufficient development length of reinforcement in joints.
• this type of failure due to erthquick because of horizontal movement of structure.

ANS - 1(C)

Observations:

• Cracks are exactly at the joint of column-beam.

CAUSE OF FAILURE:

• it's Plastic hinge failure.
• the damage occured only in the joint zone first of all.
• cyclic lateral loading & stress reversal at the joints led to the damage.

ANS - 2(A)

Observations:

• Concrete damaged at top of a column.
• concrete damaged all around the column face.
• beams are safe.

CAUSE OF FAILURE:

• it's soft storey failure, technically plastic hinge formation.
• Based on the development of crush of concrete, it can either be repairable or non-repairable.

ANS - 2(B)

Observations:

• Concrete developed complete breakage diagonally.
• Longitudinal reinforcement are intact.

CAUSE OF FAILURE:

• it's a pure shear failure.

ANS - 2(C)

Observations:

• Column failed completely.
• Failure at top of column.

CAUSE OF FAILURE:

• It's Short Column failure
• an additional slab or a beam connected to a column in mid height leads to this effect.
• this type of failures are not repairable.