Identification of Cracks

Question 1

a) What is the mode of failure or damage of the beams in the figure above? Elaborate

Observations

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

Mode of failure/damage

• Its form of flexural failure due to reversal of stress during earthquake.
• During stress reversal support top experiences compression and support bottom experiences tension
• Top compression is managed by slab advantage. Bottom tension not satisfied by the provided reinforcement.

Are the damages repairable?

• Since the reinforcement got yielded it cannot be repaired.

b) What is the mode of failure or damage of the beams in the figure above? Elaborate

Observations

• Cracks along beam-column edge.
• Cracks seem to have developed through the structure as it looks much wider.
• Beams look separated from the column at joints.
• Concrete is not severely crushed.

Mode of failure/damage

• 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 detached the beam member from column.

Are the damages repairable?

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

c) What is the mode of failure or damage of the beams in the figure above? Elaborate

Observations

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

Mode of failure/damage

• Its a plastic hinge failure.
• Damage occurred only in the joint zone first of all.
• Cyclic later loading and stress reversal at he joints led to this 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 crack.

Are the damages repairable?

• The joint can be strengthened.

Question 2

a) What is the mode of failure or damage of the beams in the figure above? Elaborate

Observations

• Concrete damaged at top of column.
• Concrete damaged all around the column face.
• Beams are safe.
• The location of column looks at the edge of building.
• No walls are built along the column means it is probably ground floor,car parking area.

Mode of failure/damage

• Its a Soft storey failure Technically,plastic hinge formation.
• Due to absence of infill walls at the ground floor plastic hinge forms at the top of ground storey column during lateral movement.

Are the damages repairable?

• Based on the development of crush of the concrete it is either repairable or non- repairable.

b) What is the mode of failure or damage of the beams in the figure above? Elaborate

Observations

• Concrete developed complete breakage diagonally.
• Longitudinal reinforcement are intact.
• Shear reinforcement spacing is wider so less number of shear rebar provided.

Mode of failure/damage

• Its a pure shear failure.
• Inadequate provision of shear reinforcement compels concrete to take all shear stresses.

c) What is the mode of failure or damage of the beams in the figure above? Elaborate

Observations

• Column failed completely.
• Failure at the top of column.
• There are two slabs connecting to column probably one at midheight.
• The wooden piles might be a post failure support to temporarily prop the column avoiding entire collapse of the structure.

Mode of failure/damage

• Its a short column failure.
• An additional column/beam connected to this column at midheight leads to this effect.
• This leads to failure if the connection is unintentional and not accounted in design.

Are the damages repairable?

• This is not at all repairable.