Identification of Cracks

Question 1:

a)

Observations :

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

Answer :

• Its a form of Flexural failure due to reversal of stress during earthquake
• During stress reversal, Support top experiences Compression and bottomexperiences the Tension.
• Top Compression is managed bySlab and Bottom tension was not satisfied by tje provided reinforcement.
• Since the reinforcement got yirlded , It can not be repaired

b)

Obsevation :

• Cracks are along Beam - Column edge.
• Crack seems to be developed through the structure as it looks wider.
• Beam looks seperated from the column at joints.
• Concrete is not severely crushed.

Answer :

• Its beampull out failure due to insufficient development lengthof reinforcement in joints.
• During Earthquake, The horizontal movement of structure makes this condition worse and detached the column member from column.
• Providing anchorage length between two existing concrete is very difficult, so not repairable

c)

Observation :

• 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's a plastic hinge failure.
• The damage occured only in the joit zone
• Cyclic lateral loading and stress reversal at the joints led to the damage
• The joint can be strengthened
• Even the slab participated to its best to handle the Tension but unable to control damage

Question 2:

a)

Observations :

• Concrete damaged at the top of a column
• Concrete damaged all around the column fzce.
• Beams are safe
• The location of te column looks at the edge of the building
• No walls are built along the column means it is probably at Groumd floor, for parking car movement access.

Answer :

• It is a soft storey failure that is plastic hinge formation
• Due to absence of infill walls at the ground floor, the plastic hinge forms at the top of the ground storey columns during lateral movements.
• Based on the developmet of crush of concreteit can either be repairable or Non - repairable.

b)

Observation :

• Concrete developed complete breakage diagonally
• Longitudinal reinforcements are intact
• Shear reinforecement spacing looks wider

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 column
• The wodden piles might be a post failure support after column failed, providing temporary prop to avoid collapse of entire structure.

Answer :

• It is a short column failure
• An additional slab or a beam connected to a column in mid - height leads to its effect
• This leads to failure especially if the connection os unintentional and not accounted in design.
• The failure given in the picture is not at al repairable