Identification of Cracks
Question 1:
a)
OBSERVATION-
- concrete crushed and reinforcement is exposed
- concrete spalled beyond the reinforcement which may be sign of rupture
- beam top portion looks safe because of the flange advantage from slab
- the cracks develop from bottom to top means rebar yielding occur in support bottom only.
ANSWER-
- Its form of flexural due to reversal of stress during eathquake.
- during stress reversal, support top experiences compression and bottom experiences tension
- top compression is managed by slab advantage, bottom tension was not satisfied by the provided reinforcement
- since the reinforcement got yielded, it cannot be repaired.
b)
OBSERVATION -
- cracks along beam column edge
- crack seems to have developed through the structure as it look much wider
- beam looks seperated from the column at joints
- concrete is not severly crushed
ANSWER -
- Its beam pull out failure due to insufficiant development length of reinforcement in joints.
- during earthquake, the horizontal movement of structue makes this condition worse and detached the beam member from column
- providing achorage length btween two existing concrete is very difficult, so not repairable.
c).
- 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
- Its a plastic hinge failure
- the damage occured only in the joint zone first of all
- the cyclic lateral loading and stress reversal at the joints led to the damage
- even the slab participated to its best to handle the tension ( slab is severly cracked means it has undegone tension with its flange conditions), but unable to control the damage
- the joint can be strengthened
Question 2:
a).
- 
OBSERVATIONS-
- concrete damage at top of a 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 at ground floor, for parking car movement access.
ANSWER-
- Its a soft strorey failure, technically plastic hinge formation
- due to absence of infills walls at the gorund floor, the plastic hinge forms at the top of ground storey column during lateral movement
- based on the development of crush of concrete, it can either be rapairable or non repairable.
b).
OBSERRVATION-
- Concrete developed complete breakage diagonally
- longitudnal reinforcement are intact
- shear reinforcement spacing looks wider ( which means probably lesser shear rebar provided)
ANSWER-
- its pure shear failure
- inadequate shear reinforcement compels concrete takes all shear stresses.
c).
OBSERVATIONS-
- column failed completly
- failure at top of column
- there are two slabs connected to column, probably one mid height of the column.
- the wooden piles might be a past failure support after column failed, providing temporary prop to avoid collapse of the entire structure.
ANSWER-
- its a short column failure
- an additional slab or beam connected to column at mid height lead to this effect
- this lead to failure especially if the connection is unintentional and not accounted in design
- the failure given in the picture is not at all reapairable