Identification of Cracks

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

A.) (a).

OBSERVATIONS:

From the picture, we can see that the concrete is crushed and the reinforcement is exposed.

RESULT:

- It is a type of flexural failure due to reversal of stress during an earthquake. So during stress reversal, the support at top experiences compression and bottom experiences tension.

- At the bottom and top of the beam, main steel is provided to prevent this kind of failure.

- The damages cannot be repaired as the reinforcement has got yielded.

(b).

OBSERVATIONS:

- From the above picture we can see the cracks are along the beam-column edge.

- The concrete is not crushed badly.

RESULT:

- It is a beam pull out failure.

- This was caused due to insufficient development length of reinforcement in joints.

- It is not repairable as providing anchorage length between 2 existing concrete would be tough.

(c).

OBSERVATIONS:

- We can see from the above picture that the cracks are at the joints of column-beam.

RESULT:

- From the observation we can understand that it is a plastic hinge failure.

- In the strong column-weak beam design, beams are anticipated to develop flexural overstrength beyond the design strength and create plastic hinges at their ends.

- The damage has occured only in the joints.

- The joints can be strengthened.

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

A.) (a).

OBSEVATION:

- We can see the concrete has been damaged at the top of the column.

- Beams look safe.

RESULT:

- Hence it is a soft story failure.

- There is a plastic hinge formation.

- Its ability to be repaired or not depends on how the concrete crushes over time.

(b).

OBSERVATIONS:

- The shear reinforcement spacing looks wider.

- It looks like the concerete has developed complete breakage diagonally.

RESULT:

- It looks like a pure shear failure.

- Concrete absorbs all shear loads since there is insufficient shear reinforcement.

(c).

OBSERVATIONS:

- From the above picture, we can conclude that the column has failed completely. The failure is present at the top of the column.

RESULT:

- It is a short column failure.

- In short columns, failure takes place due to yielding, where the phenomenon is known as crushing.

- This failure in the above picture can not be repaired.