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 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
Answers:
* Its form of flexural failure due to reversal of stress during earthquake
* During stress reversal, support top experience compression and bottom experience tension
* Top compression is managed by slab advantage. Bottom tension was not satisfied by the provided reainforcement
* Since the reinforcement got yielded,it can not be repaired
1) B. Observation :
* Cracks along 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 severly crushed
Answers:
* 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 diificult.so not repairable.
1) C. Observation :
* Cracks are exactly at the joints of column beam
* Cracks in beam developed through its entire width
* Slab also developed more cracks along the beam width direction
Answers:
* its is a plastic hinge failure
* The damage only occured in the joint zone first of all
* Cyclic lateral loading & stress reversal at the joints led to the damage
* Even the slab particulated to its best to handle the tension 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
Answers:
* Its a softy storey failure, Technically plastic hinge formation
* Due to abscence 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 be either repairable or non repairable.
2) B. Observtions :
* Concrete developed complete breakage diagonally
* Longitudinally reinforcement are intact
* Shear reinforcement spacing looks widerc
Answers :
* Its a pure shear failure
* Inadequate shear reainforcement compels concrete rakes all the shear stresses
2) C. Observation :
* 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
Answers:
* 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 unintentinal and not accounted in design
* The failure given in the picture is not at all repairable.