Identification of Cracks

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

Question1:

a) observations:

• concrete spalled beyond the reinforcement it may cause rupture.
• concrete crushed and reinforcement exposed.
• The beam top looks safe being slab supports there.
• the crack develops from the bottom of the top means rebar yielding occurs in the support bottom only.

answers:

• its forms of flexural failure due to reverse stress during an earthquake,
• top compression is managed by slab but bottom compression is not satisfied with provided reinforcement.
• during stress reversal and support top experience compression, bottom experience tension,
• since the reinforcement got yielded, it can not be replaced.

b) observations:

• cracks along the beam-column edge.
• cracks seem to have developed through the structure as it looks much wider.
• beams look separated from the column points,
• concrete is not severely crushed.

answers:

• its beam pull-out failure it happens due to insufficient development length of reinforcement joints.
• during earthquake conditions, these conditions make the beam detach from the column.
• providing the anchorage length between two existing concrete is very difficult. son not repairable.

c) observations:

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

answers:

• its 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 but was unable to control the damage,
• the joint can be strengthened.

2)

a) observations:

• concrete damaged at top of the column,
• concrete damaged all along the face of the column face,
• beams are safe,
• the location of the column looks at the edge of the building.
• no walls are built along the column means it is probably on the ground floor. for parking car movement access.

answers:

• it is a plastic hinge failure,
• due to the absence of an infill wall on the ground floor, the plastic hinge formed at top of ground story column during lateral movement,
• based on the development of crushed concrete it can be either repairable or nonrepairable.

b) observations:

• concrete developed complete breaking diagonally,
• longitudinal reinforcement is intact.
• shear reinforcement spacing looks wider.

answers:

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

c)observations:

• column failed completely,
• failure at top of the column,
• there are two slabs connected to the column probably one at mid-height of the column.

answers:

• it is a short column failure,
• an additional slab or beam connected to a column in mid-height leads to this effect.
• this leads to failure, especially if the connections are unintentional and not accounted for in the design.