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 advanatage from slab.
• The crack develops from bottom to top means rebar yilding occurs in support bottom only.
  
          ANSWER :
  
  
• It's 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 repaired.
  
         b)
  
         OBSERVATIONS :
  
  
• 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 severely crushed.
  
         ANSWER :
  
  
• It's Beam pull out of 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)
  
        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 :
  
  
• It's a plastic hinge failure.
• The damage occurred only in the joint zone.
• Cyclic lateral loading and 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)
  
     OBSERVATIONS :
  
  
• Concrete damaged at top of a column.
• Conrete 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 :
  
  
• It's 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)
  
     OBSERVATIONS :
  
  
• Concrete developed complete breakage diagonally.
• Longitudinal reinforcements are intact.
• Shear reinforcement spacing looks wider (which means probably lesser shear rebar provided)
  
     ANSWER :
  
  
• It's a Pure Shear failure.
• Inadequate shear reinforecement compels concrete takes all the shear stressess.
  
   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 :
  
  
• It's 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.