Identification of Cracks

Q1)

a- Observation:-

• Concrete crushed and the reu=inforsment 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 slab.
• The Crack develops from bottom to top means rebar yielding occurs in support bottom only

Answer:-

• Its form of flexural failure due to reversal of stress during an earthquake
• During stress reversal. Support top exeriencess compression and bottom experiences tension
• top compression is managed by slab advantage. bottom tension was not satisfied by the provided reinforcement
• Since the reinforcement was yielded it can not be repaired

b- Observation:-

• Cranks along beam column edge.
• Cracks seem to have developed through the structure as it looks much wider
• Beam looks separated from the column at joints
• concrete is not severely crushed

Answer:-

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

C- Observation:-

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

Answer:

• It's a Plastic hinge failure.
• The damage occurred 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 severely 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 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 means it is probably at Ground floor, 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) Observations:

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

Answer:

• It's a Pure Shear failure.
• Inadequate shear reinforcement compels concrete takes all the shear stresses.

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 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.