Identification of Cracks

CHALLENGE 1

1.What is the mode of failure or damage of the beams?

1.Figure (a)

Observations: their concrete are crushed and their reinforcement are exposed in air. The beam is ruptured and the cracks developed from bottom to top.

Ans. It is the flexural failure due to reversal of stress during earthquake. Due to reversal stress top support behaves compression and bottom is behaves tension. Top compression is managed by slab but bottom tension was not satisfied by the providing reinforcement. Since the reinforcement is yielded it can not be repair.

2.Figure (b)

Observation: Cracks along beam column edge. Cracks seen to have developed through the structure looks much wider. Beam looks separate from the column at joint. Concrete is not severely crushed.

Ans. The beam is failure is insufficient development length of the reinforcement in joints. During earthquake, The horizontal movement of structure makes this condition worse and detached the beam member from column. Providing anchorage length between two existing concrete is very difficult. So not repairable.

3.Figure (c)

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

Ans. It is a plastic hinge failure. The damage occurred only in the joint zone first of all. Cyclic lateral loading and stress reversal at the joints led to the damage. Even the slab is participated to its best to handle the tension but unable to control the damage.

2.What is the mode of failure or damage of the column?

1.Figure (a)

Observations: Concretes are damaged at a column. Concrete damaged all around the column face but beam are safe. The location of column looks at edge of the building. No walls are built along at edge means it is probably at a ground floor, for parking care movement access.

Ans. It is soft story failure technically plastic hinged formation. Due to absence of infill walls at the ground floor, the plastic hinge forms at the top ground story columns during lateral movements. Based on the development of crush of concrete it can either be repairable or nor repairable.

2.Figure (b)

Observations: Concrete developed completed breakage diagonally. Longitudinal reinforcement is intact. Shear reinforcement spacing look wider.

Ans. It is a pure shear failure. Inadequate shear reinforcement compels concrete takes all the shear stresses.

3.Figure (c)

Observations: Column are failed completely. There are two slabs connected to the column, probably one at mid height of the column. The wooden piles might be a posted failure support after column failed providing temporary prop to avoid collapse of the entire structured.

Ans. It is a short column failure. An additional slab or a beam connected to a column in mid height leads to these effects. This leads to failure especially if the connection is unintentional and accounted in design. The failure given in the picture is not at all repairable.