Identification of Cracks

1)

From the picture it is seen that only bottom part of the beam is damaged.The top portion of beam is safe. This is due to the flange advantage of the slab. The crack develops from bottom and reaches to top i.e the rebar yeilding is in bottom alone.

Reason: This is due to the flexural failure due to reversal of stress which occurs during earthquake. During this process the top goes through compression and bottom goes through tension. But since top part has flange advantage , it is safe. the bottom however is not given enough reinforcement.

Remedy:Reinforcement is yeilded hence non repairable.

2)

From the picture it is seen that the crack is along edge of beam and column edge.The beams looks seperated from column at joints.

Reason: This is due to beam pull out failure . This is due to insufficient length of reinforcements at the joint.

This is due to earthquake's horizontal movement of structure . This detach the beam member from column.

Remedy:Its is non repairable

3)

From the picture it is seen that the cracks are exactly at joint of column beam. The cracks are also developed along the beam .

Reason: This is due to plastic hinge failure. This occurs due to cyclic lateral loading and stress reversals at joints.The slab do contribute to control the damage but it is unable to do so.

Remedy:The joints can be strengthened .

4)

From the picture it is seen that there are no walls surrounding it hence it is ground floor maybe a parking. The beams are safe . Concrete damage is only at the top of column and damage is all around the column face.

Reason: This is called short storey failure . Due to the absence of infil walls to transfer the vibration due to earthquake to the ground, plastic hinges are formed at top of ground storey .

Remedy: It can be repaired or not repaired based on the development of crush of concrete

5)

There is a complete breakage of column diagonally.Longitudinal reinforcements are still safe. But due to less shear reinforcement and fewer shear rebars , the spacing look wider.

Reason: Diagonal cracks always imply pure shear failure. This is due to inadequate shear reinforcement . They compel concrete to take all the shear stress.

Remedy:Provide more shear rebar

6)

The top column failed completely. Piles are givenas post failure support as to avoid collapse.

Reason:This is known as short column effect.Short column attracts more force than long columns during earthquake. This leads to failure.

Remedy:THis is non repairable.Short columns can be avoided as whole or made stronger.