Identification of Cracks

AIM: To identify the types of cracks from the given pictures for awareness of structural failures, distinguishing structural and non-structural cracks, observing the structural issues and understanding Seismic failures.

Ans 1.a.

Observations:

• From the picture 1 it is observed that the concrete of beam is crushed and the reinforcement is exposed
• Concrete is damaged beyond the exposed reinforcement
• There is no damage to top portion of the beam due to flange action from slab and is safe
• The cracks are developed from the bottom towards top of the beam indication reinforcement yield at the bottom of the slab

Answer:

• It is a flexural failure due to the reversal of stress due to earthquake.
• During the stress reversal the beam top support experiences compression and the bottom experiences tension
• The top compression was managed by the slab flange support, while the bottom tension was not satisfied by the provided reinforcement
• Since the reinforcement is yielded, the damage cannot be repaired.

Ans 1.b.

Observations:

• Crack is observed at the beam and column junction
• The crack seems to be developed through the structure as the crack looks wider.
• Beam looks separated from the column
• The concrete is not severely crushed

Answer:

• The beam pull-out failure due to insufficient development length of reinforcement in joints
• During the earthquake, the horizontal movement makes this condition worse and the beam is detached from the column
• Since the anchorage reinforcement cannot be provided between two existing concrete members, the failure cannot be repaired.

Ans 1.c.

Observations:

• Cracks are developed at the column and beam junction
• Crack in the beam is developed in the entire width of the beam
• Slab has also developed several cracks along the beam width direction

Answer:

• It is plastic hinge failure
• The damage has appeared only at the joint zone
• Cyclic lateral loading and the stress reversal at the joints led to the damage
• Slab is also subjected to severe stress under tension with its flange condition and the cracks are developed in the slab which could not prevent damage.
• The damage can be repaired by strengthening the joint

Ans 2.a.

Observations:

• The cracks are observed on the top area of column
• The concrete is damaged all around the column face
• The beam looks safe without any damage
• The location of the column looks at the edge of the building
• No walls are built around the column indication the location is ground floor for parking access.

Answer:

• It is a soft frame failure due to plastic hinge formation
• Due to absence of the infill walls probably at ground floor, the plastic hinge forms at the top of the columns during lateral movement
• Based on the development of the crush of the concrete the failure may be repairable or non-repairable depending on the actual inspection of the severity of damage.

Ans 2.b.

Observations:

• The column concrete developed complete breakage diagonally
• Longitudinal reinforcement looks intact
• Shear reinforcement spacing looks wider indicating less shear rebars may be provided

Answer:

• It is pure shear failure
• Inadequate shear reinforcement causes the concrete to carry additional shear stress leading to the shear failure of concrete.

Ans 2.c.

Observations:

• Column failed completely as seen in the picture
• Failure is at the top of column
• There are two slabs connected to the column probably one at mid height and other at the top of column
• The wooden props are used temporarily to support post failure of the column to avoid further collapse of the structure by supporting temporarily.

Answer:

• It is a short column failure
• An additional slab or a beam connected to a column in mid height leads to the effect.
• This leads to the failure especially if the connection is unintentional and not accounted in the design
• The failure is not repairable

CONCLUSION:

Thus we have studied the given pictures and noted the observations of the failed structures and provided the probable reasons of failures and the mentioned if the failures are repairable.