Identification of Cracks

Question 1:

a) Observation :

• Concrete is detroirated from the bottom of the beam.
• Top portion of the beam is found good due to flange from the slab.
• The rebar yielding is from bottom.

Answer:

• The failure occurs due to the reverse stress during the earthquake.
• The compression acts at the top and tension at bottom of the beam.
• The compression is supported by the slab and the tension couldn't be managed by the reinforcement which is not sufficient.
• Hence the reinforcement is yielded and cannot be repaired.

b) Observation:

• The cracks are developed along the column.
• The crack is also developed exactly at the joints of the beam and column.
• However the concrete is not crushed.

Answer:

• The failure is due to the insufficient anchorage distance between the beam and column.
• The horizontal movement of the structure during earthquake make it worse.
• Hence it cannot be repairable between the existing concrete.

c) Observation:

• The cracks are developed at the joint and along the beam.
• The crack also occured in the slab along the beam direction.

Answer:

• The cracks is is in the corner position only which is the Plastic hinge failure.
• The lateral loading and reversal stress causes the damage.
• The slab also participated in bearing the tension since the cracks are developed in slab, which is also not sufficient to manage the tension.
• This can repairable.

2.

a) Observation:

• The cracks are developed along the column.
• The beam is safe.
• There is no partition wall connected to the column.

Answer:

• This is a Plastic hinge failure.
• This is due to there is no walls at ground floor, plastic hinge occurs at top level due to lateral movement of the structure.
• This can be repairable or non-repairable based on concrete crush.

b) Observation:

• Concrete damages completely.
• The reinforcement also detroirated.
• The rebar size provided is probably not sufficient.

Answer:

• This is a total shear failure.
• This cannot be repairable.

c) Observation:

• The column is totally failed and damaged.
• Two slabs are connected to the column.
• The slab is supported with the wood pipes to support the column.

Answer:

• This is due to the structure is not accounted in the design.
• This failure is due to the short column.
• This cannot be repairable.