Identification of Cracks

1(a)

In the figure, it is showed that the concrete cracks are found and the reinforcement is exposed. But the top of the beam was uncracked and the crack was developed from bottom to top of the beam which means reinforcement yielding occurred at the bottom.

It is formed due to flexural failure because of reversal of stress during earthquake. During stress reversal, top of the concrete experience compression and bottom experience tension. The compression was managed by concrete that is the slab, it act as a flange but bottom tension was managed by the reinforcement at the bottom but it gets yielded, so it cannot be repaired

1(b)

Cracks were seen at the beam column edge. Concrete is not severely crushed, beam looks separated from the column at joints. Cracks seem to have developed through the structure as it looks much wider.

This condition is due to the insufficient development length of reinforcement in the joints, so beam pull out failure. When horizontal movement of structure during earthquake this failure will occur, that moment the beam is detached from the column took place. It is not repairable because providing anchorage length in the existing concrete sections is very difficult.

1(c)

Cracks are exactly at the joint of column beam. Cracks in beam developed through its entire width. Slab also developed more cracks along the beam width direction

It’s a Plastic hinge failure. The damage is occurred at the joint, so cyclic lateral loading and stress reversal at the joints led to the damage. Slab shows severe damage it means that it has undergone tension with its flange condition but unable to control the damage. It can repaired by strengthening the joint.

2(a)

Concrete damaged around the column face, it seen that the column location is at the edge of the building. The top beam was seen safe. It may be a car park area or the ground floor of a building without infill wall.

It is a soft storey mechanism failure. The plastic hinge was formed at the top of the ground floor columns during lateral deformation due to the absence of infill walls. So the weak column and strong beam mechanism, column will fail. It can either be repairable or non-repairable.

2(b)

Complete breakage of concrete was showed in the picture. Longitudinal reinforcements are intact. Reinforcement shortage was seen.

This is due to the shear failure. In adequate shear reinforcement was provided at the column. So concrete should takes all the shear stresses. This cannot repairable.

2(c)

Complete column failure. There are two beams connected to the column. One of the beam at the mid height and other at the top of the column. The wooden piles are provided to support the column after failure to avoid collapse of the entire structure.

It’s a Short Column failure. An additional slab or beam at the mid height leads to this effect. If the connection is unintentional and not accounted in design then total collapse of the structure happens. It is not repairable.