Identification of Cracks

Question 1:

a)

Observations:-

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

Answer:-

• Its form of flexural failure due to reversal of stress during earthquake.
• During stress reversal,support top experieces compression and bottom experiences tension.
• Top comression is managed by slb advantage bottom tension was not satisified by the provided reinforcement.
• Since the reinforcement got yielded, it can not be repaired.

b)

Observations:-

• 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 jonts.
• Concrete is not severely crushed.

Answer:-

• its beam pull out failure due to in sufficient development length of reinforcement in joints.
• During earthquake, the horizontal movement of structure makes this condition worse and detached the beam member from column.
• providing anchorage length between two existing concrete is very difficult.
• So not repirable.

c)

Observations:-

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

Answer:-

• It's 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 it's best to handle.the tension (slab is severely cracked means it has undergone tension with it's flange condition), but unable to control the damage.
• The joint can be strengthened.

Question 2:

a)

Observations:-

• Concrete damaged at top of the 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 accesss.

Answer:-

• It's a safe storey failure, technically plastic hinge formation
• due to the absence of inill 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
• In adequate 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 failue support after column failed, providing temporary prop to avoid collapse of 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 the failure especially if the connection is un intentional and not accounted in design.
• The failure given in the picture is not at all repairable.