Identification of Cracks

1a) OBSERVATION

• Concrete is crushed and reinforcemnet is exposed
• Concrete spalled beyond reinforcement , maybe a sign of rupture
• the top of the beam portion looks safe because of the flange advantage from slab
• the crack develops from bottom to top means rebar yeilding occurs in support bottom only

ANSWER

• this is a form of flexural failure due to reversal of stress during earthquake
• during stress reversal ,support top experiences compression and bottom experiences tension
• top comoression is managed by slab advantage but bottom tension was not satisfied by provided reinforcemnet
• since reinforcemnet yeilded, it cant be repaired

1b) OBSERVATION

• cracks are along beam column edge
• cracks seem to have developed through the structures as it looks much wider
• baam looks separated from column and joints
• concrete is not severely crushed

ANSWER

• it is a beam pullout failure due to insufficient development length of reinforcement in the beam
• dueing an earthwuake, the horizontal movement of structure makes this condition worse and detaches the beam member from the column
• providing anchirage length between 2 existing concrete structutres is difficult ,hence not repairable

1c) OBSERVATION

• cracks are exactly at the joint of beam column
• cracks in beam developed through its entire width
• slab also developed more cracks along the beam width dircetion

ANSWER

• its a plastic hinge failure
• the damage occured only in the joint zone
• cyclic lateral loading and stress reversal at the joints led to the damage
• even the slab participated its best to handle tension but unable to control the damage
• this joint can be strengthened

2a)OBSERVATION

• concrete damaged at the top of teh column and all around the column face
• beams are safe
• location of the column looks at the edge of the building
• no walls are built along the column means it is probably at the ground floor for parking

ANSWER

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

2b) OBSERVATION

• concrete developed complete breakage diagonally but longitudinal reinforcements are intact
• shear reinforcement spacing looks wider

ANSWER

• its a pure shear failure
• inadequate shear reinforcement compels concrete to take all the shear stresses

2c) OBSERVATION

• column failed completely at the top
• there are 2 slabs connected to column, probabaly one at mid height of the column
• the wooden piles might be a post failure support after column failed, providing temporary props to avoid collapse of teh 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 teh connection is unintentional and not accounted in design
• the failure given in the picture is not atall repairable