Identification of Cracks

1)

AIM:

To observe the given situations of various modes of failure and to comment on them if the damages are repairable or not.

PROCEDURE:

a)

OBSERVATIONS:

• We can see that the reinforcement in the beam is exposed, as concrete cover has got crushed.
• Concrete that got spalled beyond the reinforcement may be caused due to rupture.
• Beam's top portion looks uncracked and is safe because of flange support from the slab.
• Here, the cracks appears to be started from bottom, this means the rebar yielding occurs in bottom support only.

COMMENTS:

• It is a form of flexural failure due to reversal of stress during earthquake.
• Compression in the top is managed by slab but the bottom tension was not satisfied by the reinforcement provided.
• As the reinforcement got yielded here, it can not be repaired.

b)

OBSERVATIONS:

• Here, cracks are developed along beam-column edge.
• Wider cracks are developed.
• Beam looks seperated from the column at the joints.
• Concrete is not severely crushed as seen in the above case.

COMMENTS:

• It is Pull Out failure, which occurs due to insufficient development length provided.
• During Earthquake, the horizontal movement of structure makes the situation more worse and it may also detach the member from the column.
• Since providing anchorage length between two already existing concrete members is very difficult, hence it is not repairable.

c)

OBSERVATIONS:

• Here, cracks are exactly at the joint of column and beam.
• Cracks in beam are developed throughout its entire width .
• Slab also developed more cracks along the beam width direction.

COMMENTS:

• It is Plastic Hinge failure.
• The damage occured mainly in the joint of the column and the beam.
• Cyclic lateral loading and stress reversal at the joint led to the severe damage at the joint.
• Even the slab took part to handle the tension (Slab is severely cracked that means it has undergone tension with its flange condition), but was unable to control the damage.
• The joint can be strengthened, hence the damage is repairable.

RESULT:

Observations have been made for the following situations provided and are commented if the damage is repairable or not, and also the justification for the same has been made.

2)

AIM:

To observe the given situations of various modes of failure and to comment on them if the damages are repairable or not.

PROCEDURE:

a)

OBSERVATIONS:

• Concrete got damaged at the top of the column.
• Concrete is damaged all around the column face.
• Damage occured only to columns but beams are safe.
• The location of column looks like it is at the edge of a building.
• No walls are built along the column that means it is probably at the ground floor, for parking or car movement access.

COMMENTS:

• It is a soft storey failure, technically known as plastic hinge formation.
• Due to absence of infill walls at the ground floor, the plastic hinge forms at the top of the ground storey columns during lateral movement.
• Based on the magnitude of development of crush in the concrete members, it can either be repairable or non-repairable.

b)

OBSERVATIONS:

• Concrete developed complete cracks and got crushed diagonally.
• Longitudinal reinforcements are intact even after the damage.
• Shear reinforcement spacing looks wider (which probably means lesser shear rebar is provided than required).

COMMENTS:

• We can see diagonal cracks in the figure, which means it is a pure shear failure.
• Inadequate shear reinforcement compels concrete to take all the shear stresses.
• It is not possible to repair this type of failure after the damage.

C)

OBSERVATIONS:

• Column shown in the figure is failed completely.
• Failure is occured at the top of the column.
• There are two slabs connected to the column, probably one at the mid height of the column.
• The wooden piles might be a post failure support provided after the column got failed, providing temporary support to avoid collapse of the entire structure.

COMMENTS:

• It is a short column failure.
• An additional slab or a beam connected to the column in mid-height leads to this effect.
• This leads to failure especially if the connection is unintentional and not accounted in the design.
• The failure that can be seen in the picture is not at all repairable.

RESULT:

From the observations that are made, we have commented if the damages are repairable or not and the proper justification for the same has been made.