Identification of Cracks
1) (a)
OBSERVATIONS:
Concrete crushed and the reinforcement is exposed.
Concrete spalled beyond the reinforcement which may be a sign of Rupture.
Beam top portions look safe because of the flange advantage from slab.
The crack develops from bottom to top means rebar yielding occurs in support bottom only.
ANSWER:
It is a Flexural failure due to reversal of stress during Earthquake.
During a stress reversal Top support experiences as "Compression' and Bottom support experiences as "Tension".
Top compression is managed by slab advantage but the Bottom tension is not satisfied by the provided reinforcement.
Since the reinforcement got yielded, it not be repaired.
1) (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 joints.
Concrete is not severely crushed.
ANSWER:
Its Beam pull out failure due to insufficient deveopment 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 repairable.
1) (c)
OBSERVATIONS:
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.
Cyclic lateral loading & Stress reversal at the joints led to the damage.
Even the slab participated to its best to handle the Tension (Slab is severely cracked means it has undergone tension with its fange condition). But unable to control the damage.
The joint can be strengthened.
2) (a)
OBSERVATIONS:
Concrete damaged at top of a 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 access.
ANSWER:
Its a Soft storey failure. Technically Plastic hinge formation.
Due toabsence of Infill walls at the ground floor. The plastic hinge forms at the Top of ground storey columns during Lateral movement.
Base on the development of crush of concrete. It can either be rpairable or Non- repairable.
2) (b)
OBSERVATIONS:
Concrete developed complete breakage diagonally.
Longitudinal reinforcements are intact.
Shear reinforcement spacing looks wider (which means probably lesser shear rebar provided)
ANSWER:
Its a Pure Shear failure.
Inadequate shear reinforcement compels concrete takes all the shear stresses.
2) (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 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 a Beam connected to a Column in mid-height leads to this effect.
This leads to failure especially if the connection is unintentional and not accounted in design.
The failure given in the picture is not at all repairable.