Identification of Cracks

1.

a)

Observation

• Concrete crushed and the reinforced is exposed.
• Concrete spalled beyond the reinforcement which may 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.

Result & Conclusion

• 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 by slab advantage. Bottom tension was not satisfied by the provided reinforcement.
• Since the reinforcement got yielded, it can not be prepaired.

b)

Observation

• 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.

Result & Conclusion

• Its beam pull out failure due to insufficient development 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.

c)

Observation

• 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.

Result & Conclusion

• It's 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 flange condition), But unable to control the damage.
• The joint can be strengthened.

2.

a)

Observation

• Concrete damaged at the top of a column.
• Concrete 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.

Result & Conclusion

• It is a soft storey failure, technically plastic hinge formation.
• Due to absence of infill walls at the ground floor, The plastic hinge forms at the top of ground storey columns during lateral movement.
• Based on the development of crush of concrete, it can either be repairable or non-repairable.

b)

Observation

• Concrete developed complete breakage diagonally.
• Longitudinal reinforcements are intact.
• Shear reinforcement spacing looks wider (which means probably lesser shear rebar provided)

Result & Conclusion

• It is a pure shear failure.
• Inadequate shear reinforcement compels concrete takes all the shear stresses.

c)

Observation

• Column failed completely.
• Failure at top of column.
• There are two slabs connected to the column. Probably one at mid height of column.
• The wooden piles might be a post failure support after column failed, providing temperory prop to avoid collapse of the entire structures.

Result & Conclusion

• It is a column failure.
• An additional slab or a beam connected to a column in mid-height leads to the effect.
• This leads to failure especially if the connection is unintentional and not accounted in design.
• Not repairable.