Identification of Cracks

Ans 1 (a):

Observation made: The damage is happened at an edge of the beam, resulting in Cracking and Spalling of concrete cover.

• Bottom R/F can be seen, with no shear links along the distance of spalling though length of cracks is significant.
• vertical crack at an edge is reaching to the full depth of beam, concrete confinement is negligible now-onwards.
• Minute crack can be identified easily at the column face.

Conclusion:

Flexural Damage of beam section is identified as it originates from the bottom portion of the beam towards inner side of beam.

Flexural Damage is mostly associated with Cracking & spalling of concrete along with Yielding of bars. By contrast, Flexural Failure comes with disintegration of concrete beyond its cover, often with Buckling (or) even Rupture of bars. Such effect is mostly happened at the bottom face of the beam because at the top, Slab and beam monolithic connection have significant restraint in Flexure through concrete & Steel availability.

Remarks: Such Damage happened because of poor detailing of beam section resulting in poor concrete confinement at the beam's core.

Repairing can be done in aesthetic form but section cannot be reiterated again.

Provide More closely spaced Shear Stirrups to a distance of about 2d from the face of the column.

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Ans 1(B):

Observation: Cracks seen in column section seem to be hair line cracks deteriorating the plaster surface over the column.

• Cracking & Spalling of Concrete cover can be identified on the Right side of the picture in column.

Conclusion:

Such Cracks should be identified in the beam section resulting due to Plastic Hinging instead of Beam-column Joint. Insufficient detailing of beam Column elements, resulting in yielding of column first.

strong Column-Weak Beam Mechanism can provide cure to such type of issues.

Remarks: Such Damage can be Repaired but Detailing cannot changed resulting in similar condition at the arrival of cons equal earthquake.

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Ans 1(c):

Observation Made: The vertical cracks are passing at the Beam Column joint, towards the full depth of a beam.

• Column joint is completely affected by such crack which is unacceptable.
• Crack on the right side of the beam in (pic c) have significant width which keep on increasing with Reversal of Cyclic Loading resulting in Yielding of Bottom R/F or even Rupture of steel Bars.

Conclusion:

Such Damage in Column section shall not be accepted anywhere in the structural components of any building.

Poor Ductile Detailing in the beam-column joint results in yielding of section at the joint which is supposed to be took place at the proximity of beam edge with hair line cracks.

Remark: Such Damage cannot be repaired, if done Crack get widened again & again with every Cycle of Stress Reversal resulting in Yielding of Bottom R/F or even Rupture.

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Ans 2 (a):

Observation: Yielding of Column section under the beam shows Strong Beam & weak column concept.

concrete cover spalling took place near the beam- column Joint.

Conclusion: these are Non-Structural spalling of concrete which is repairable and has no significant reduction in strength & stiffness of members.

Remarks: These cracks get avoided by placing the beam at the centre of a core of Column section.

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Ans 2(b):

Observation: Concrete Cover burst out at the centre of the column.

• Concrete Core get scattered out Completely inside the Core of a column.
• Spacing of Stirrups should be checked out first before manifestation.

Conclusion: Such Cracks take place due to inability of Concrete to bear the compression.

Compression Failure of Concrete, it’s a region favourable for splicing of Column members so Longitudinal r/f have no Role in this failure.

Remarks: such Failure can be avoided by adopting Good Grade of Concrete, or by Increasing the Column Dimensions.

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Ans 2 (c):

Observation Made: Complete Failure of Column at the top side of Beam-Column joint.

• Shear Failure Of concrete at the top of column.
• Four Longitudinal bars are running along the length of column.
• No Closely Spaced stirrups are found near the Beam-Column Joint.

Conclusion: Inadequate Modelling in a frame leads to such catastrophic failure. Columns are quite Slender in section as compared to beams Resulting in Weak Column & Strong Beam.

In case Keeping the same configuration, R/f Detailing in column has to be improved or increase the configuration of Column section.

Concrete Grade seems to be very poor.

Remarks: Can not be repaired, failed up to that much extent that "unserviceable".