Identification of Cracks

Q.1 a)

ans:

Observation:

Fig 1 shows that concrete crushed and reinforcement is exposed.cracks developed from bottom to top means rebar yielding occures at support bottom only i.e. R/F is still active at support top.

ans:

Its form of flexural failure due to reversal of stress during earthquake. during stress reversal,support top exeprienced compression and bottom experiences tension.

TOP compression is managed by the slab advantages.bottom tension was not satisfied by the provided reinforcement,since the reinforcement got yieled . it can not br repaired.

b)

Observation:

Crack along edge (beam column),developed through structure as it look much wider . beam looks seperated from column at joints.concrete is not severly crushed.

ans:

Its beam pull out failure due to insufficient development lenght of R/F in joints.During earhquake horizontal fmovement of sructure makes this condition worse and detached the beam member from column. Providing anchorage lenght between two existing concrete is very difficult, so not rapairable.

c)

Observation:

cracks are exactly at the joint of column beam. crack in beam developed through its width. slab also developed more crack along the beam width direction.

ans:

Its a plastic hinge failure. damaged occured only in the joint. cyclic lateral loading and stress reversal at the joints led to the damage. Even the slab participated to its best to handle the tension but unable to control the damage.

the joint can be strengthen.

Q.2

a) obervation:

1. concrete damaged at op of column .
2. concrete damaged all around the coulmn face beam are safe.
3. the location of column looks at edge of the building.
4. no walls are built along the column means it is probably at ground floor ,for parkin car access.

ans:

1. Its plastic hinge formation.
2. due to absence of infill walls @ the ground floor the plastic hinge forms at the top of ground storey column during lateral movement.
3. based on the development of crush of concrete it can either be repairable or non repairable.

b)

observation:

1. concrete developed complete breakage diagonally.
2. longitudinal R/F are intact.
3. shear R/F spacing looks wider.i.e less shear rebar provided.

ans:

1. its a pure shear failure .
2. inadaquate shear R/F comples concrete takes all the shear stress.

c)

observation:

1. column failed completely.
2. there are two slabs connected to the column, probably are at mid height of the column. the wooden piles might be a post failure support after column ,providing temporary prop to avoide collapse of the entire structure.

ans:

1. Short column failure.
2. additional slab or beam connected to column in mid height leads to this effect.
3. it leads to failure specially if the connection is unintetional and not accounted in design.failure is not at all reparable.