Identification of Cracks

1. What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate

Aim: We have to find out the mode of failure or damage.

Introduction: To know how to observe a structural issue. And understanding Seismic Failures.

a)

Observations:

• In the given picture/image the concrete of the beam is broken and the reinforcement is visible to the eyes.
• The rupture may occur because the concrete is spalled behind the reinforcement.
• No cracks and damage is found at the top of the beam because of the slab so it is safe from the top of the beam.
• Crack in the beam is increases from bottom to top and the crack is not at the top due the tensile strength of the reinforcement.

Conclusions:

• This kind of failure is Occur due to the reversal of stress during earthquake and it is a kind of flexural failure.
• It is mainly occur due to compression in top and tension in bottom
• The reinforcement at the bottom is not sufficient to resist the tension in the beam and the top compression is resist the by the slab so there is no crack in the top.

Is it Repairable ?

It is not be repairable because the bottom portion i.e. reinforcement has lost their elastic limits or the reinforcement get yielded.

b)

Observations:

• In this image the Cracks are seemed at the edges or the bottom of the Column and beam.
• It looks like the column and the beam joint are separated from each other (circled at the image).
• The cracks are seemed to be much wider than the normal
• The concrete is not so severely damaged

Conclusions:

• The rebars length provided at the beam is not sufficient to the anchor (Insufficient Anchorage of the rebars), so this the reason of the failure.
• The column joint are separated because of the horizontal movement of structure during earthquake.

Is it Repairable ?

No, because it is very difficult to provide the anchorage length of the rebars between to existing concrete.

c)

Observations:

• In this image the cracks are formed at the joint of the Column and Beam.
• the cracks occur at the entire width of the beam.
• In the Slab the cracks are developed at the width direction of Beam.
• In the beam the cracks are developed to the parallel of the width

Conclusions:

• It is a Plastic hinge failure
• The Plastic hinge failure is developed only at the joint so the main damage is occur at the joint zone.
• The main reason is due to Cyclic loading and stress reversal at the joints led to the damage.
• Slab is severely cracked due to the tension that is the cracks at the slab defining that slab has tried to handle the tension but it ins not under control.

Is it Repairable ?

Yes, the Junction of the Column and beam is to be strengthened.

2. What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate

Aim: We have to find out the mode of failure or damage.

Introduction: To know how to observe a structural issue. And understanding Seismic Failures.

2(a)

Observations:

• The column is at the edge of the building.
• The image shows that the concrete is damaged at the top of the column near the column beam joint.
• Around One face of the column is damaged.
• No defects are found in the beams.
• No walls are built along the column so it means it is the Ground Floor area

Conclusions:

• From these observations its clear, this is a soft storey failure, technically plastic hinge formation at colum
• Due to lateral movement in the building and absence of walls, columns got affected because of plastic hinge formed at the upper side of the ground floor

Is it Repairable ?

Based on the development of crush of concrete it can be either be repairable or non-repairable.

2(b):

Observations:

• The concrete is detached from the column
• It is not a crack it is completely crushed.
• The breakage of the concrete is developed diagonally
• All the reinforcement are visible
• The rebars are not damage seemed in the image.
• The shear reinforcements were not sufficient so it had detached

Conclusions:

• By the observation of the image the failure is Pure Shear failure because all the concrete is detached.
• The shear reinforcement compels concrete and take all the shear stresses due to lesser shear reinforcement.

2(c):

Observations:

• In the image the Column is seemed to be failed completely.
• The failure is occur at the top of the column.
• By the wooden piles the temporary support is allow to avoid the Complete structure failure.
• The two slabs are connected to the column, i.e. one at mid height clearly visible

Conclusions:

• The failure is observed as Short Column failure.
• Due to the intermediate Slab provided the heavy shear load is affected to the column, this occur the column failure.
• The intermediate slab load is unintentional and not accounted in the design so this leads to the failur

Is it Repairable ?

This failure will not be repairable.