Identification of Cracks

1. (a) Observations:

• Concrete crushed and the reinforcement is exposed.
• Concrete spalled beyond the reinforcement which may bea sign of rupture.
• Beam top portion looks safe beacuse of the flange advantage from slab.
• The crack develops from bottom to top means rebar yeindling occurs in support bottom only.

Conclusion:

• It is a form of Flexural Failure due to reversal of stress during earthquake.
• During Stress reversal, support top experiences Compression and bottom experiences tension.
• To compression is managed by Slab advantage. Bottom tension was not satisfied by the provided reinforcement.
• Since the reinforcement got yeilded, it cannot be repaired.

(b) Observations:

• Cracks along Beam-Column Edge.
• Cracks seem to have developed through the structure as it look much wider.
• Beam looks seperated from the column at joints.
• Concrete is not severely crushed.

Conclusion:

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

(c) Observations:

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

Conclusion:

• It is a Plastic Hinge Failure.
• The damage occured only in the joint zone first of all.
• Cyclic lateral loading and stress reversal at the joints led to the damage.
• Even the slab participated to its best to handle the tension, because the slab is severely cracked means it has undergone tension with its flange condition. But unable to control the damage.
• The joint can be strengthned.

2(a) Observations:

• Concrete damaged at top of the Column.
• Concrete damaged all around the column Face.
• Beams are safe and undamaged.
• The location of column looks at the edge of the building.
• No walls are built along the column means it is probably at Ground Floor, for parking car movement access.

Conclusion:

• It is a Soft storey failure. Technically Plastic Hinge Formation.
• Due to abscence of Infill walls at the Ground Floor, the plastic hinge forms at the Top of Ground store columns during the Lateral Movement.
• Bsed on the development of crush of concrete it can be either be repairable or Non-repairable.

(b) Observations:

• Concrete developed complete breakage diagonally.
• Longitudinal reinforcements are intact.
• Shear reinforcement spacing looks wider which means probably lesser shear rebar is provided in the columns.

Conclusion:

• It is a Pure Shear Failure.
• Inadequate shear reinforcement compels concrete takess all the shear stress.

(c) Observations:

• Column failed completely.
• Failure at top of column.
• There are two slabs connected to the column. Probably one at mid height of the column.
• The wooden piles might bea post failure support after column failed, providing temporaty prop to avoid collapse of the entire structure.

Conclusion:

• It is a Short Column Failure.
• An additional slab or a beam connected to a column in mid-height leads to this effect.
• This leads to failure especially if the connection is unintentional and not accounted for in design.
• The failure given in the picture is not at all repairable.