Identification of Cracks

1)a) Observations:-

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

Answer:-

• Its form of Flexural failure due to reversal of stress during earthquake.
• During stress reversal, Support top experiences compression and bottom experiences tension.
• Top compression is managed by slab advantage. Bottom tension was not satisfied by the provided reinforcement.
• Since the reinforcement got yielded, It can not be repaired.

b) Observation:-

• Cracks along beam column edge.
• Cracks seems to have been developed through the structure as it looks much wider.
• Beam looks seperated from the column at joints.
• Concrete is not severly crushed.

Answer:-

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

c) Observation:-

• Cracks are exactly at the joint of column and beam.
• Crack in beam developed through its entire width.
• Slab also developed more cracks along the beam width direction.

Answer:-

• Its a plastic hinge faliure.
• The damage only occured in the join zone.
• Cyclic lateral loading & stress reversal at the joints led to the damage.
• Even the slab participated to its best to handle the tension (Slab is severally cracked means it has undergone tension with its flange condition). But unable to control the damage.
• The joint can be strengthened.

2)a) Observation:-

• Concrete damaged at top of a column.
• Concrete damaged all around the column face.
• Beams are safe.
• The location of column looks at edge of the building.
• No walls are built along the column menas it is probably at ground dloor for parking car movement access.

Answer:-

• It's a soft storey failure, Technically plastic hinge formation.
• Due to absence of infill walls at the ground floor, the plastic hinge forms at the top of ground storey columns during lateral movement.
• Based on the development of crush of concrete it can either be repairable or Non-repairable.

b) Observation:-

• Concrete developed complete breakage diagonally.
• Longitudinal reinforcement are intact.
• Shear reinforcement spacing looks wider(Which means probably lesser shear rebar provided)

Answer:-

• It's a pure shear failure.
• Inadequate shear reinforcement comples concrete takes all the shear stresses.

c) Observation:-

• Column failed completely.
• Faliure at top of column.
• There are two slabs/Beam connceted to the column, Probably one at mid height of the column.
• The wooden piles might be a post failure support after column failed, Providing temporary prop to avoid collapse of the entire structure.
• The vertical reinforcement has been crancked.

Answer:-

• It is a short column failure.
• An additional slab or a beam connceted to a column in mid-height leads to this effect.
• This leads to failure especailly if the connection is unintentional and not accounted in design.
• The reinforcement quality has to be increased and the thickness.
• The failure given in the picture is not at all repairable.