Identification of Cracks

1a-

Observations-

• The concrete on the beam is crushed and the reinforcement is exposed.
• The damage occurs at the end and bottom of the beam.
• Top of the beam looks safe due to flange advantage from slab.
• The cracks occurs from the bottom to top which means yielding of bars occurs at the bottom.

Answer-

• Flexural failure occurs due to the reverse of stress during earthquake,
• Here the top experienced tension and bottom experienced compression.
• The top compression was managed by the slab concrete but the bottom tension could not be managed by the reinforcement provided.
• Since the reinforcement is yielded the structure cannot be repaired.

1b-

Observations-

• Cracks occurs along the beam-column edge.
• Concrete looks cracked but not crushed.
• Cracks appeared to have developed through the structure as it looks much wider.

Answer-

• Beam pull out failure due to insufficient development length has occurred here.
• Since providing the anchorage length or development length is very hard in an already existing structure, this looks like not repairable.

1c-

Observation-

• Cracks appear at the joint of the beam-column.
• Cracks have developed through the entire width of the beam.
• Cracks have also occurred in the direction of the beam in slab

Answer-

• Since the failure occurs at the joints of the beam-column this could be plastic hinge failure.
• This occurs due to cyclic lateral loading and stress reversal at the joints.
• The slab provided some strength to manage the failure by undergoing tension but failed since some cracks are developed.
• The structure can be strengthened therefore it is repairable.

2a-

Observation-

• Failure occurs at the top of the column.
• Concrete seems to be crushed and the whole face of the column is damaged.
• Beam seems fine.
• No wall means either ground floor, basement level, parking space.

Answer-

• Since it is at bottom It could be soft storey failure or plastic hinge failure.
• Since there are no in fill walls during lateral movement plastic hinge occurs at the top of the ground storey columns.
• Based on the development of the crushed concrete it can be determined whether the structure is repairable or not.

2b-

Observations-

• Concrete appears to be severely damaged.
• Although the longitudinal reinforcements seem intact, but the shear reinforcement spacing is very wide.

Answer-

• It is a pure shear failure.
• the failure occurred due to providing inadequate reinforcement to the structure.

2c-

Observations-

• columns is completely failed.
• Columns also seem detached to the beam.
• Two slabs are attached to the column one at top and one in mid columns and both are detached as cracks can also be observed in mid column.
• The wooden pile are post failure support system for the beam.

Answer-

• It looks like a short column failure.
• The addition of the beam or slab at middle may be the cause.
• The addition of the beam or slabs leads to unintentional loads which are not accounted for in the design and can lead to failure.
• The column looks severely damages and cannot be repaired.