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 beam? Would you categorize the case as a damage or as failure? Are the damage repairable? Elaborate
a)
Type: Damage
Cause: Flexural cracks developed at bottom of beam
Explanation: Damage have occurred at the beam column joint. The beam have undergone severe damage as compared to Column. Here the beam will yield prior to the column. The beam has insufficient cover at the bottom of the 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: may have happened due to use of high slump concrete. And due to not using proper compacting techniques like vibrator or may be due to any vibrating loads which acted on it.
Can be repaired by adding grout to the surface of coloum
c)
Type: Damage
Cause: Beam column connection/joint failure
Explanation: May be due to short column weak beam. Here the beam formed plastic hinges at undesirable locations and developed more flexural strength beyond the required/desired strength which lead to this.
Can be repaired temporarily and 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 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.
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 designed by considering design factors.
Failure can be rectified by retrofit techniques.