Identification of Cracks

Challenge 1

Q1:

a)

Observations

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

Results

• It is a form of flexural failure.
• It is 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 and bottom tension was not satisfied by the provided reinforcement.
• Since the reinforcement got yielded, it cannot be repaired.

b)

Observations

• The cracks are along the beam and column edges.
• The cracks seem to have developed through the structure as it looks much wider.
• The beam looks separated from the column at joints.
• The concrete is not severely crushed.

Results

• It is a beam pull out failure.
• It is due to insufficient development length of reinforcement in joints.
• During earthquake, the horizontal movement of the 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

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

Results

• It is a plastic hinge failure.
• The damage only occurred in the joint zone.
• The cyclic lateral loading and stress reversal at the joints led to the damage.
• The slab is severely cracked, which means it has undergone tension with its flange condition, but unable to control the damage.
• The joint can be strengthened.

Q2:

a)

Observations

• The concrete is damaged at top of the column.
• The concrete damaged all around the column face.
• No damage for beams.
• The location of the 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.

Results

• It is a soft storey failure, technically plastic hinge formation.
• It is due to the 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)

Observations

• The concrete developed completely breaked diagonally.
• The longitudinal reinforcements are intact.
• The shear reinforcement spacing looks wider, which means probably lesser shear rebar provided.

Results

• It is a pure shear failure.
• Inadequate shear reinforcement compels concrete takes all the shear stresses.
• It is not repairable.

c)

Observations

• The column failed completely.
• The failure is at the top of the 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.

Results

• 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 in design.
• The failure given in the picture is not at all repairable.