Identification of Cracks

Question 1:

a) b)  c) 

What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate

 ANS:

1(a)

Observations from image:

1.The Failure has happen at beam column joint.

2.The crack happened at the bottom of the beam.

3.The concrete crushed and the reinforcement is exposed.

4.Concrete spalled beyond the reinforcement which may be a sign of rupture.

5.Beam top portion looks safe because of the flange advantage from slab.

6.The crack develops from bottom to top means rebar yielding occurs in support bottom only.

Answer:

1.Its form of Flexural failure due to reversal of stress during earthquake.

2.During stress reversal, Support top experiences Compression and Bottom experiences tension.

3.Top compression is managed by Slab advantage. Bottom tension was not satisfied by the provided reinforcement.

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

1 b)

observations:

1. Cracks along Beam-Column edge.
2. Cracks seem to have developed through the structure as it looks much wider.
3. Beam looks separated from the column at joints.
4. Concrete is not severely crushed.

Answer:

1. Its Beam pull out failure due to insufficient development length of reinforcement in Joints.
2. During earthquake, The horizontal movement of structure makes this condition worse and detached the beam member from column.
3. Providing anchorage length between two existing concrete is very difficult. So not repairable.

1.c

Observations:

1. Cracks are exactly at the joint of Column- Beam.
2. Cracks in Beam developed through its entire width.
3. Slab also developed more cracks along the beam width direction.

Answer:

1. It's a Plastic hinge failure.
2. The damage occurred only in the joint zone first of all.
3. Cyclic lateral loading & stress reversal at the joints led to the damage.
4. Even the slab participated to its best to handle the Tension (Slab is severely cracked means it has undergone tension with its flange condition), But unable to control the damage.
5. The joint can be strengthened.

 Question 2:

a)  b)  c)