Identification of Cracks

1.a) Observation of Failure:

i.Concrete crushed and the reinforcement is exposed.

ii.Concrete spalled beyond the reinforcement which may be the sign of rupture.

iii.Beam top portion looks safe because of the flange advantage from slab.

iv.The damage occured because of rebar yielding in support bottom only by means of cracks developed from bottom to top.

Solution:

i.Its a form of flexural failure due to reversal of stress during earthquake.

ii.During stress reversal, support top experiences compression and bottom experiences tension.

iii.Top compression is managed by slab advantage. Bottom tension was not satisfied by the provided reinforcement.

iv.Since the reinforcement got yielded, it cannot be repaired.

1.b) Observation of Failure:

i.Cracks were formed along the Beam-Column edge.

ii.Cracks seem to have developed through the structure as it looks much wider.

iii.Beam looks seperated from the column at joints.

iv.Concrete is not severly crushed.

Solution:

i.Its beam pull out failure due to insufficient development lenght of reinforcement in joints.

ii.During earthquake, the horizontal movement of structure makes this condition worse and detached the beam member from column.

iii.Providing anchorage length between two existing concrete is very difficult and hence it is not repairable.

1.c) Observation of Damage:

i.Cracks are exactly at the joint of Column-Beam.

ii.Cracks in beam developed through its entire width.

iii.Slab also developed more cracks along the beam width direction.

Solution:

i.Its a plastic hinge failure.

ii.The damage occured only in the joint zone first of all.

iii.Cyclic lateral loading and stress reversal at the joint led to this damage.

iv.Even the slab participated to its best to handle the tension (slab is severely cracked means it undergone tension with its flange condition). But unable to control the damage.

v.The joint can be strengthened.

2.a) Obseravtion of Failure:

i.Concrete damaged at top of column.

ii.Concrete damaged all around the column face and beams are safe.

iii.The location of column looks at the edge of the building.

iv.No walls are built along the column means it is probably at ground floor for car parking movement access.

Solution:

i.Its a soft storey failure, technically plastic hinge formation.

ii.Due to absence of infill walls at the ground floor, the plastic hinge forms at the top of ground storey columns during lateral movement.

iii.Based on the development of crush of concrete it can either be repairable or non-repairable.

2.b) Observation of Failure:

i.Cracks developed complete breakage diagonally.

ii.Longitudinal reinforcemnet are intact.

iii.Shear reinforcement spacing looks wider (which means probably lesser shear rebar provided i.e spacing of ties is larger).

Solution:

i.Its a pure shear failure.

ii.Inadequate shear reinforcement compels concrete takes all the shear stresses.

iii.Since the longitudinal rebars are not damaged, it can be repairable.

2.c) Obseravtion of Failure:

i.Column failed completely.

ii.Failure at top of column.

iii.There are two slabs connected to the column, probably one at mid height of the column.

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

Solution:

i.Its a short column failure.

ii.An additional slab or a beam connected to a column in mid-height leads to this effect.

iii.This leads to failure especially if theconnection is unintentional and not accounted in design.

iv.The failure given in the picture is not possible to repairable.