Identification of Cracks

1. Aim:To identify the failure of the column or beam and to justify whether the failure is replaceable or nonrepairable.

a. Observations:

• From the above figure 'a' the beam got damaged in the junction of the column and beam and the beam is damaged in the bottom layers.
• The top portion of the beam is safe due to the presence of the flabge action in the slab .
• The cracks are being developed from bottom to top of the beam.The concrete is spalled beyond the main reinforcement of the beam and the beam failure is generally caused due to the rupture.
• The top reinforcement of the beam is in the acctive condition only. so it doesnot created any faiure.

Causes of failure:

• The failure of the beam is due to the stress reversal due to the earth quake.
• Due to the earthquake the reversal force occur to the structure and due to these reversal stress the beam may subject to the tension in the bottom fibres and the compression in the top fibres.
• The reinforcement provided may be less and it unable to with stand the stress caused due to the earthquake and the cause the failur of the beam.
• The main reinforcement is totally damaged and it is a non repairable.

b. Observations:

• From the given figure 'b' the cracks are developed in the junction of the column and beam, the cracks are developed on the entire length of the beam and column junction.
• The cracks developed are wider by the visual appearence.
• The concrete was not heavily damaged.

Causes of the failure:

• The failure of the beam is due to the insufficient development length of the main reinforcement of the beam.
• Due to the shortage of the anchorage length of the main reinforcement when the beam is subjected to the lateral movement caused due to the earthquake or ground motion.
• The increase in the anchorage length for the main reinforcement in the beam is very difficult and it is not rpairable or non replaceable.
• Foe better architural appearence the cracks developed in the structure are generally packed with the sealing agent.

c.Observations:

• For the beam the cracks are developed in the junction of the column and beam through out the entire width of the beam.
• The slab also participates to take over the tension due to the flange action and so the cracks are developed for the slab along the beam length direction.

Causes of the failures:

• The cracks are developed due to the plastic hinge formation and the plastic hinge generally formed at the support or at the junction of the column and beam.
• These type of the cracks are generally formed due to the circular lateral loading or due to the reversal stress caused for the beam and column junction.
• More over the slab controls the tension to some extent but it should fails to control the tension to its full extent.
• The Joint can be strengthened by the suitable technique.

2. Aim:To identify the failure of the column or beam and to justify whether the failure is replaceable or nonrepairable.

a. Observations:

• The concrete has ruptured on the entire surface of the column on all the sides.
• The beams are safe from the formation of the cracks.
• The columns are the outer side and there is no connection with the walls that means these are the columns at the ground floor or at the car parking area.

Causes of the failures:

• This is soffit storey failure and this failure is caused due to the pplastic hinge formation.
• Due to the absence of the walls between the columns the lateral movement created for the building may cause th plastic hinge formation and leads to the formation of the cracks.
• Based on the severity of the crushing of the concrete the column can be strengthened.

b. Observations:

• The concrete is ruptured on the entire surface of the beam.
• The main bars in the column are intact due to the more load.
• The shear reinforcement is very less than the required, the spacing between the shear reinforcement of the column is very high and it creates the shear failure.

Causes of the failure:

• Due to the less amount of the shear reinforcement and it is a purely shear failure.
• During the execution the shear reinforcement is not provided according to the codal requirements.
• The increase in the shear reinforcemnt is very difficult and the structure or the column is not repairable.

c. Observations:

• The column is totally damaged.
• The column is damaged at the top at which the column is in connection with the slab.
• Two slabs are in contact with the column and it seems that the salb may also be damged.
• The wooden supports are provided temporarily to prevent the sudden collapse of the entire structure.

Causes of the failure:

• This is a short column failure.
• Provision of the second slab to the column at the mid height may cause this kind of the effect.
• The failure is caused due to the double slab provision that the design of the column is done with the one slab.
• This failure cannot be repaired at any extent.