Identification of Cracks

AIM: Identification of Cracks

INTRODUCTION:

There are two types of failure modes in reinforced concrete beams: flexural failure and shear failure. The former occurs when the imposed load exceeds the flexural capacity of the beam's materials, whereas the latter occurs due to a lack of shear resistance between the beam's materials.

TASK 1: What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate.

a)

Type: Damage

Cause: Flexural cracks developed at bottom of the beam

Explanation:

• Damage has occurred at the beam-column joints. The beam has undergone severe damage as compared to the Column. Here the beam will yield prior to the column. The beam has an insufficient cover at the bottom of beam.
• This can be repaired before becoming a failure. Can be rectified by providing proper cover at the joints.

b)

Type: Damage

Cause: Honeycombing in concrete

Explanation:

• This may have happened due to the use of high slump concrete. And due to not using proper compacting techniques like a vibrator or may be due to any vibrating loads which acted on it.
• This Can be repaired by adding grout to the surface of the column.

c)

Type: Damage

Cause: Beam column connection/joint failure

Explanation:

• Maybe due to short column weak beam. Here the beamformed plastic hinges at undesirable locations and developed more flexural strength beyond the required/desired strength which lead to this.
• This Can be repaired temporarily and has a high chance of changing from damage to failure.

TASK 2: What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate.

a)

Type: Failure

Cause: Failure of column due compression

Explanation:

• Due to the high compressive load acting on the column, the column will fail without undergoing any lateral deformation. The concrete gets crushed and the steel will yield and then column failure occurs.
• The main objective here will be to keep the newly generated stress under the permissible limit.

b)

Type: Failure

Cause: Shear failure

Explanation:

• In the absence of shear walls in a structure/ building, the lateral loads will be completely carried by the columns. Lateral loads can be in the form of wind, earthquake loads, etc.
• This is actually a design failure and was supposed to be provided provisions at the time of designing itself, like shear links or sections to carry the shear forces.

c)

Type: Failure

Cause: Short column failure

Explanation:

• The short column is subjected to compressive stresses and thus it fails due to crushing. Should have been designed by considering design factors.
• Failure can be rectified by retrofit techniques.

CONCLUSION:

From the above challenge, we know the mode of failure or damage of the beams.