Identification of Cracks

1 a) Observation:

· Concrete crushed and reinforcement is exposed

· Concrete spalled beyond the reinforcement which man=y be a sign of rupture

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

· The crack develops from bottom to top means rebar yielding occurs in support bottom only

Answer:

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

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

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

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

b) observation

· Cracks along the beam- column edge

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

· Beam looks separated from the column at joints

· Concrete is not severely crushed.

Answer :

· Its Beam pull out failure due to insufficient development length of reinforcement in the joints

· During the earthquake, the horizontal movement of the structure makes this condition worse and attached the beam member from column

· Providing anchorage length between 2 exiting concrete is very difficult. So not repairable.

c) Obersvation:

· Cracks are exactly at the joint of the column beam

· Crack in beam developed thro its entire width

· Slab also developed more crack along the beam width direction

Ans:

· It’s a plastic hinge failure

· The damage occurred 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 flange condition). But unable to control the damage

· The joint can be strengthened.

2 a) Observation

· Concrete damaged at top of a column

· Concrete damaged all around the column face

· Beams are safe

· The location of the column looks like it at the edge on the building

· No walls are built along the column means it is probably at the ground floor, for parking areas

Answer

· It’s a soft storey failure, technically plastic hinge formation

· Due to absence of Infill walls at the ground floor. The plastic hinge forma at he Top of ground storey columns during lateral movement.

· Based on the development of crush of concrete, it can either be repairable or Non repairable.

2 b) Observation

· Concrete developed complete breakage diagonally

· Longitudinal reinforcements are intact

· Shear reinforcement spacing looks wider (which means probably lesser shear rebar provided)

Answer

· It’s pure shear failure

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

2 c) Observation :

· Column failed completely

· Failure at the top of column

· There 2 slabs connected to the column Probably one at mid height of the column

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

Ans:

· It’s a short column failure

· An additional slab or 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.