Identification of Cracks

What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate

Question 1:

a)

observations:

• Concrete is 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 advantange from slab
• The crack develops from bottom to top means rebar yielding occurs in support bottom only

Mode of Failure:

• Its form of flexural failure due to reversal of stress during earthquake
• During stress reversal, support top experiences compression and bottom experiences tension
• Top compressiom is managed by slab advantage. Whereas bottom tension was not satisfied by the provided reinforcement
• Since the reinforcement got yielded, it cannot 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

Mode of Failure:

• Its beam pull out faialure due to insufficient developmetn length of reinforcement in joints
• During eathquake, the horizontal movement of structure makes this condition worse and detached the beam member from column
• Providing the 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

Mode of Failure:

• It's a plastic hinge failure
• The damage occurred only in the joint zone first of all
• Cyclic lateral loading and stress reversal at the joints led to the damage
• Even the slab participated to its best to handle the Tension but cracked by undergoing tension with its falnge condition and unable to control the damage
• This damage can be repaired by strengthening the joint

Question 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

Mode of Failure:

• It's a soft storey failure, due to formation of plastic hinge
• Due to absemce 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, that is lesser shear rebar is provided for the column

Mode of Failure:

• It's a pure shear failure
• Inadequate shear reinforcement compels concrete takes all the shear stresses.
• The size of the columns is increased in the direction of shear to increase the shear capacity.

c)

Observations:

• Column is failed completely
• Failure occured 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 suppport to avoid collapse of the entire structure

Mode of Failure:

• 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 occured is not repairable