Identification of Cracks

1)What is the mode of failure or damage of the beams in the figure Below? Are the damages repairable? Elaborate

a)

Observations from the Image:

• 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 slab.
• The crack develops from bottom to top means rebar yielding occurs in support bottom only.

Answer:

• It's a form of Flexural Failure due to reversal of stress during earthquake.
• During stress reversal support top where usually in tension will experiences compression and bottom experiences tension.
• Top compression is managed by slab advantage and the Bottom tension was not satisfied by the provided reinforcement.

Is the Damage Repairable:

• Since the reinforcement got yielded, it can not be Repaired

b)

Observations from the Image:

• Cracks along Beam-Column edge.
• Cracks seem to have developed through the structure as it looks much wider.
• Beam looks seperated 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 horizontall movement of structure makes this condition worse and detached the beam member from column.

Is the Damage Repairable:

• Providing anchorage length between two existing concrete is very difficult. So not repairable.

c)

Observations from the Image:

• 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.

Answer:

• 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.

Is the Damage Repairable:

• 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)What is the mode of failure or damage of the beams in the figure Below? Are the damages repairable? Elaborate

a)

Observations from the Image:

• 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 wall are built along the column means it is probably at ground floor for parking car movement access.

Answer:

• It is 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.

Is the Damage Repairable:

• Based on the development of crush of concrete, it can either be repairable or Non-repairable.

b)

Observations from the Image:

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

Answer:

• It is a Pure Shear failure.
• Inadequate shear reinforcement comples concrete takes all the shear stresses.

c)

Observations from the Image:

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

Answer:

• 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.

Is the Damage Repairable:

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