Identification of Cracks

OBSERVATIONS:

• Cracks have developed along the edges of the beam-column joints.
• Cracks are very wide as can be seen in the picture indicating the severity of the condition.
• The beam-column connection is affected and the beam looks detached from the column.

MODE OF FAILURE:

• It is a form of beam-columns connection failure.
• This occurs due to the insufficient development length provided while designing the structure.
• So, the deficient development length leads to loosening the beam-column joint due to which cracks occur and the beam is pulled out of the column ultimately.

IS IT REPAIRABLE?

• NO! Since it is a completed structure, it is very difficult to provide anchorage at the beam-column joints. Hence, this failure cannot be repaired.

c)

OBSERVATIONS:

• Severe cracks at the beam-column connection joint.
• More cracks on the beam than on the columns indicating the plastic behavior of the beam.
• Sizeable random cracks on the slab surface can also be seen that seem to be along with the beamwidth.

MODE OF FAILURE:

• It is a plastic hinge failure as only the beam is effected by cracks and not columns.
• Plastic hinge first appears in the beams before columns making it a strong column weak beam mechanism.
• Cyclic lateral loading and stress reversal can lead to this plastic hinge damage as seen in the picture.

IS IT REPAIRABLE?

• YES! The beam-column joint can be strengthened and the structure can be brought back to normal.

QUESTION 2:-

a)

OBSERVATIONS:

• Column top portion is damaged excessively.
• The crushing has taken place on all four sides of the column.
• Beams are totally safe indicating stronger beams and weaker columns.
• No walls are attached to the column indicating it is a ground floor level used for parking etc.

MODE OF FAILURE:

• The mode of failure, in this case, is the soft storey mechanism.
• We can see in the picture that the beams are completely fine which projects the strong beam weak column connection.
• So, in the soft storey mechanism, the plastic hinge instead of being evenly distributed across the structural geometry is limited to a single story. Due to this, columns of that particular story are subjected to excessive stresses leading to such a type of failure.

IS IT REPAIRABLE?

• Depends on the crushing of concrete. If large a portion of the concrete has been crushed in this failure, the repair is not possible.
• On the other hand, repairs can be done for the damage limited to a certain level of concrete crushing.

b)

OBSERVATIONS:

• The concrete has been completely crushed and the entire reinforcement is visible.
• Large diagonal cracks are visible on the column surface.
• Longitudinal reinforcements are intact indicating it is not a compression failure.

MODE OF FAILURE:

• It is a complete shear failure.
• Inadequate shear reinforcement placing has led to this destruction.
• Stirrups spacing is more than recommended which is also one of the reasons for the damage caused.

IS IT REPAIRABLE?

• NO! Concrete has been crushed completely due to the excessive shear force. Therefore, it would be more economical to cast a new column rather than repair this one.

c)

OBSERVATIONS:

• The column has completely detached from the beam and slab leading to an absolute column failure.
• The column is no longer in a position to support the beam resting on it.
• You can see an additional slab attached to the column at mid-height.
• As a result, temporary wooden props are installed to hold the beam still for some time.

MODE OF FAILURE:

• It is a classic example of short column failure.
• Due to connecting an additional slab at mid-height of the column, the lateral forces exceed the shear strength of the column.
• This leads to the complete column failure if special design considerations have not been made by the engineer for such scenarios.

IS IT REPAIRABLE?

• NO! The column has completely been detached from the structural geometry. Therefore, it can't be repaired anymore.