Identification of Cracks

1.A

Observations

• Concrete is broken and the reinforcement at the bottom is exposed.
• The concrete is broken due to failure of reinforcement.
• The top reinforcement is still active due to the slabs reinforcement.
• The cracks developed from the bottom to the top it means the reinforcement is yielded at the bottom.

Conclusion.

• It is a flexural failure due to earthquake.
• Generally Top experience tension and Bottom experience Compression. But during Earthquake the top experience compression and it can withstand by the slabs with beam having flange like connection.
• But the bottom experience tension which cannot be handled by the reinforcement provided.
• Hence the reinforcement is yielded and it cannot be repaired.

1.B

Observations

• Cracks developed at the beam column joint.
• Concrete is not broken.
• But the cracks developed are seen longer.
• The beam is separated from the column.

Conclusion

• Its beam pull out failure due to insufficient development length of reinforcement at the joints.
• During earthquake the horizontal movement of the structure makes the beam and column to detach.
• Providing anchorage reinforcement between two columns is very difficult so it is not repairable.

1. C

Observations

• Cracks are developed at the joints of beam column.
• The cracks are developed to the width of the beam
• Slabs also developed cracks along the beam width direction.

Conclusion

• This is the plastic hinge failure. Formation of plastic hinge at undesired location.
• The cracks are created only in the joints.
• These type of cracks are generated due to high shear force during the seismic activities.
• Even the slab also helps to control the tension, but unable to control the tension. It develops cracks.
• The joint is strengthened.

2.A

Observation

• Concrete is damaged at the top of the column.
• Beams are not damaged, even no cracks are seen in the beam.
• Concrete is damaged all around the column.
• No wall is built in between the column. Thus it is a parking space or ground floor.

Conclusion

• It is a weak column strong beam failure, due to soft storey mechanism.
• The plastic hinge is developed at undesired location.
• Due to no walls connected at the ground floor columns the plastic hinge formed at the top of the column in ground floor.
• Based on the spalling of concrete it can either be repairable or non-repairable.

2.B

Observation

• Concrete is completely damaged along the longitudinal direction.
• The longitudinal reinforcement are intact.
• The shear reinforcement are spaced wider.

Conclusion

• It is purely shear failure.
• Inadequate shear reinforcement will lead the concrete to take all the shear force and leads to spalling of concrete.

2.C

Observation

• Column failed completely.
• Column failed at the top.
• There are two slab levels connected to the column probably one is service level and other is floor level slab.
• The wooden piles are provided post failure of column to support the beam to avoid the collapse of entire structure.

Conclusion

• It is a short column failure
• An additional slab or beam connected to the mid-level of the column leads to this effect.
• This failure is especially due to unintentional and unaccounted slab in the mid height of column during design.
• It is not repairable.