Identification of Cracks

1.

a)

OBSERVATION :

• The concrete looks crushed and the Reinforcements are exposed to air.

• The concrete spalled beyond the reinforcement which may the sign of rupture.

• The beam top portion looks safe because of the flange advantage from slab.

• The crack develops from bottom to top means rebar yield occurs in support bottom only.

ANSWER :

• It is the form of flexural failure due to reversal of the stress during earthquake.

• During the stress reversal, the top of the support experiences compression and the bottom experiences the tension.

• The top compression is managed by the slab advantage and also the bottom tension was not satified by the provided reinforcement.

• Since the reinforcement got yielded, it can not be repaired.

1.

b)

OBSERVATION :

• The Cracks formed along Beam-Column edge.

• The Cracks seem to have developed through the structure as it looks much wider.

• The Beam looks separated from the column at joints.

• The concrete is not severely crushed.

ANSWER :

• Here, it is a beam pull out failure due to insufficient development length of reinforcement in joints.

• 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, it is not repairable.

1.

c )

OBSERVATION :

• The cracks are exactly at the joint of column-Beam.

• Cracks in beam developed through its entire width.

• Slab also developed more cracks along the beam with direction.

ANSWER :

• Here, it is a 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.

• Even the slab participated to its best to handle the tension (When a slab is severely craked means it has undergone tension with its flange condition). But unable to control the damage.

• The joint can be strengthened.

2.

a)

OBSERVATION :

• Concrete damaged at top of a column .

• Concrete damaged all around the column face.

• Beams are safe.

• The location of the 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 :

• It is a soft storey failure, technically a plastic hinge formation.

• Due to absence of infill walls at the ground floor, the plastic hinge forms at the top of ground storey columns during lateral movement.

• Based on the development of crush of concrete, it can either be repairable or Non-repairable.

2.

b)

OBSERVATION :

• Concrete developed complete breakage diagonally.

• Longitudinal reinforcements are intact.

• Shear reinforcement spacing looks, wider (which means probably lesser shear rebar provided).

ANSWER :

It is a pure shear failure.

Inadequate shear reinforcement compels concrete takes all the shear stresses.

2.

c)

OBSERVATION :

• Column failed completely.

• Failure at top of the 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, providing temprorary prop to avoid collapse of thee entire structure.

ANSWER :

• It is a short Column failure.

• An additional slab or a beam connected to a column mid-height leads to this effects.

• This leads to failure especially if the connection is unintensional and not accounted in design.

• The failure given in the picture is can not be repairable.