Identification of Cracks

1(a)

Observations:

• Concrete crused and the reinforcement is exposed.
• Concrete spalled beyond the reiforcement which may be a sign of rupture.
• Beam top portion looks safe because of the flange advantage from slab.
• The crack develops from bottom top means rebar yielding 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 nt satisfied by the provided reinforcement.
• Since the reiforcement got yielded, it can nt be repaired.

1(b)

Observations:

• Cracks along Beam-Column edge.
• Cracks seem to have developed throungh 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 joints.
• During earthquake, the horizontal movement of strucutre make this condition worse and detached the beam member from column.
• Providing anchorage length between two existing concrete is very difficult. So not repairable.

1(c).

Observations:

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

Answer:

• Its a plastic hinge failure.
• The damage occured only in the joint zone first of all.
• 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 severly cracked means it has undergone tension with its flange condition), But unable to control the damage.
• The joint can be strengthened.

2(a)

Observations:

• Concrete damaged at top 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 means it is probably at ground floor, for Parking car movement access.

Answer:

• It's a soft story 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 cursh of concrete, it can either be repairable or Non-repairable.

2(b)

Observation:

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

Answer:

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

2(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 be a post failure support after column failed, providing temporary prop to avoid collapse of the entire structure.

Answer:

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