Identification of Cracks

1.

a.

 

Answer:- 

Observation:- 

• Concrete crushed and reinforcement is exposed
• Concrete spalled beyond the reinforcement which may be sign of rupture
• The top portion of the beam looks like safe because of the flange advantage from the slab
• The crack develops from the bottom to top means the rebar has reached its plastic state at bottom portion

Result:- 

• It's a form of flexural failure due to reversal of the stress during earthquake
• During stress reversal, structure top experiences the compression and bottom experiences the tension
• Top compression is satisified with slab advantage and bottom tension was not satisified by the provided reinforcement
• Since the reinforcement got yielded, it can't be repaired

 

b.

 

 

Answer:- 

Observation:- 

• The cracks are present along the beam - column edge
• Crack seems to have developed through structures as it looks much wider
• Beam looks sperated from the column at joints
• Concrete is not severely crushed

Result:- 

• It's a beam pullout failure due to insufficient development length of reinforcement in joint
• During earthquake the horizontal movement of the structure makes this condition worse and detached the beam member from the column
• Providing anchorage length between two existing concrete in very difficult. so not repairable

 

c.

 

Answer:- 

Observation:- 

• Cracks are exactly at the joint of the column - beam
• Cracks in width developed through its entire width
• Slabs also developed more cracks along the beam width diretion

Result:- 

• It's a plastic hinge failure (If the failure occure at the joint of the beam is considered as a plastic hing failure and cyclic lateral loading and stress reversal led to this joint)
• The damage occure only at the joints
• Cyclic lateral loading and stress reversal led to this joint
• Even the slab participated to handle the tension but unable to controal the damage
• The joint can be strengthened 

 

2.

a.

Answer:- 

Observation:- 

• Concrete damaged at top of the column
• Concrete damaged at all around the column face
• Here Beams are safe
• The location of the column looks like it is present outside the buiding
•  No walls are built along the column means it's probably at the ground floor which is used for parking 

 

Result:- 

• It's a softstory failure and it's a plastic hinge formation
• Due to absence of infill walls at the ground floor, The plastic hinge form at the top of ground floor storey column during lateral movement
• Based on the development of crush of concrete, it can either repairable on non-repairable

 

b.

 

Answer:- 

Observation;- 

• Concrete developed complete breakage diagonally 
• Longituudinal reinforcement are intact
• Shear reinforcement looks wider

Result:- 

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

 

c.

 

Answer:- 

Observation:- 

• Cloumn failed completely 
• Failure at top of column, probably one at mid height of the column
• Wooden pile might be post failure supported after column failed, providing temporary prop to avoid collapse of the entire structure

Result:- 

• It's a short column failure
• An adiitional slab or beam are connected to the column in mid height leads to this effect 
• This leads to failure especially if the connection is unintentional and not accounted in design
• The faillure given in picture is not at all repairable