Identification of Cracks

1 a) OBSERVATIONS:

• Concrete crushed and the reinforcement is exposed
• Concrete spalled beyond the reinforcement which maybe 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:

• It is form of flexural failure due to reversal of stress during earth quake
• During stress reversal ,support top experiences compression and bottom experiences tension
• Top compaction is managed by slab advantage .bottom tension was not satiesfied by the provided reinforcement
• Since the reinforcement got yielded it can not be repaired

1 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

ANSWERS:

• It is beam pull outfailure due to insufficient development length of reinforcement in joints
• During earth quake the horizontal movement of structure makes this condition worse and detached the beam member from column
• Providing anchorage length between two excisting concrete is very difficult . so not repairable

1 c) OBSERVATIONS:

• Cracks are excatly at the joint of column beam
• Cracks in beam developed through its entire width
• Slab also developed more cracks along the beam width direction

ANSWERS:

• It is 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 severly 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 damage at top of a column
• Concrete damaged all around the column face
• Beam is safe
• The location of column looks at the edge of building
• No walls are built along the column means it is probably at ground floor for parking car movement access

ANSWERS:

• It is a soft storey failure , Techincally plastic hinge formation
• Due to absence of infill wall at the Ground Floor ,the plastic hinge forms at the top of ground storey columns during internal movement
• Based on the development of crush of concrete it can either be repairable or non repairable

2 b) OBSERVATIONS:

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

ANSWERS:

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

2 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

ANSWERS:

• It is 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 unintentionally and not accounted in design
• The failure given in the picture is not all repairable