Identification of Cracks
Question 1. What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate.
Answer.
1(a):
OBSERVATION:
- We can clearly seen in the above image that the damage is done with beam but the column is perfectly fine.
- The damage is more caused to the beam than the column.
- In this above image we can clearly see that the layer of concrete is completely crushed and reinforcement is clearly visible or we can say reinforcement is exposed.
- Concrete is damaged beyond the reinforcement which we can say that it may be a sign of rupture.
- We can clerly see in the above image that the bottom of the beam is totally damaged but we can also see that the top of the beam is totally fine maybe because of the flange of the slab.
- In the above image we can see that the cracks are developed from the bottom to the top which means the rebar yielding occurs at the bottom of the beam only.
RESULT:
- From the above observations we can say that the cracks are formed due to the flexural failure in the beams.
- Before going to the point that the failure is repairable or not first lets understand what is flexural failure, so mostly flexural failure occurs when the loads on the beam exceeds its flexural capacity.
- So if the loads increases beyond its flexural capacity,then it will cause the flexural failure.
- So from the above observations it can be seen that due to the yielding of the steel reinforcements,the failure can not be repaired because the yielding members can not carry loads anymore.
- A steel plate covered with chemical anchors can be provided at the junction to act as the secondary reinforcements for the concrete beam.
- So according to the above observations wecan say that the repair for this crack can not be done due to the high yielding of the steel reinforcement.
1(b):
OBSERVATION:
- So we can clearly see in the above image that the failure that is occuring in the above image is along the Beam-column edge.
- We can say that this failure may occurs due to the mistake that was done during the construction process.
- In the above figure we can clearly see that the concrete of the beam and the column is not much damaged or we can say that the concrete of the column and the beam is not severly crushed.
- It can be seen that the failure have developed through the structure.
- The beam which is the horizontal member,it looks detached from the column at the joints. This can be clearly seen in the above image.
RESULT:
- So from the above observation we can conclude that this failure occurs due to the Beam Pull out.
- Now before proceeding whether it is repairable or not first lets understand what is Beam Pull out failure. So basically beam-pull out failure is a failure mode in which the anchors pull out of the concrete without the development of the full steel or concrete capacity.
- It is clearly be seen in the image that this failure is a beam pull out failure as the beam is clearly pulled out from the column.
- So a normal anchorage between the column and the beam should provide reinforcement bends with enough development length to maintain the connectivity.
- So in this case it is not possible to provide the anchorage between the long span.
- As we all know that the connectivity of the member is purely depend on the construction phase of the project.
- And it is also very difficult to provide normal anchorage between the beam and the column at a large span so it is not possible to repair this failure.
- And we can say that it is very difficult to repair this failure becaiuse in order to provide enough connectivity between the members,we must need a series of clamps in the form of the anchor bolts, but it will be more difficult to provide clamps as it requires spacing in order to provide series of clamps.
- So in short we can conclude that the repairing of this failure is not possible.
1(c):
OBSERVATION:
- As we can see in the above image,this crack occurs at the beam-column joint. The black area which we can see in the above figure is the area of the failure that occurs at the beam-column joint.
- And the failure seems around the width of the beam.
- As we can see that the failure can be seen around the width of the beam we can also say that the slab also experience the failure,and the failure in the slab indicates that the tension forces was very high.
RESULT:
- So from the above observation we can conclude that this failure occurs due to the Plastic hinge.
- So now before concluding anything we must understand what is Plastic hinge failure.
- So the plastic hinge failure is the failure which occurs only on the elastic portion of any structural members.
- So we can conclude that this failure is repairable. Because this type of failure can be expected during the designing phase. It is repairable because it occurs at the plastic hinges of the structure.
- So we have to design the structure in such a way where undesirable large forces can be transfered into a desired location,so that the cost of the building and its effectiveness can be achieved.
- So in short we can repair this failure by strengthening the joints can be done to ensure that the cracks will no longer increase.
Question 2. What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate.
Answer.
2(a):
OBSERVATION:
- As we can see in the above image that this failure only occurs around the column member only.
- According to this image the only the column is affected but the beam of this structure is perfectly fine. There is no damage to the beam structure.
- This type of the damage occurs on the column occured due to the lack of the effective force transfer throughout the stucture. This can happen only when the columns are spaced muc h far away and the beams are provided at the higher place to provide the space.
- By seeing the above image we can say that this column and beam must be place in the ground floor or the parking floor as we can see in the above image that there is no wall attached to the beam and the column. And there is much space at there sides we can say that this must be placed at the parking area or the ground area.
- As we can see that there are no walls around the columns so thats why we can assume that this column may be located at the ground floor maybe for the parking area.
RESULT:
- So from the above observation we can conclude that this failure is a Plastic hinge failure or the soft storey failure.
- So because there is no infill walls around the column at the ground level,so the plastic hinge will form at the top of the ground storey columns.
- So if we talk about whether this failure is repairable or non-repairable then we can say according to the above observations that it is completely depends on the severity of the column spanning only,with that consideration only then we can conclude whether the failure is repairable or not.
- So we can say that this type of failure depends on the intensity of the damage that is done by the column member.
- If the column member is intact not affected and there is no effect on the reinforcement or yielding during the seismic event then only we can consider that this failure can be still repaired and strengthened.
- But if the cracks on the columns are more than severe,and the flexural failure occurs on the column then we can conclude that the failure can not be repaired.
- Or we can say that it is not possible to repair thr failure at this moment because of the severity of the failure.
2(b):
OBSERVATION:
- What we have seen in the above image that the column member is severly crushed.
- We can see that the damages in the column is done in the lateral direction which means the direction of the breakage or the damage is diagonal which means shear force caused the damages to the columns.
- It is also possible that due to the lacking of the horizontal ties breakage on the concrete may have caused.
RESULT:
- This failure is a pure example of the Pure shear failure.
- In the above image we are able that the column does not have horizontal ties to restrain the shear force,so a failure occurs diagonally where the shear force applied.
- As we can see that the column is severly crushed so it is not possible to repair this failure.
- The concrete is already broken,so a new structure must be provided in order to support the remaining parts of the columns which is still unaffected.
- But there is no chance to repair this failure.
2(c):
OBSERVATION:
- In the above image we can see that the failure occurs at the top beam member of the column.
- It is the complete disjointment.
- It can be clearly seen that this column is no longer able to withstand the loads therefore, the wood support has been provided in order to support the slab.
- This wood support can be treated as the temporary solution in order to avoid the collapse of the whole structure.
- In the above image we can see that there is another intermediate slab also which is connected to the damaged column at somewhat height in the middle i guess.
RESULT:
- This failure is the pure example of short column failure.
- Mostly this type of the failure occurs where there is uncalculated forces that will applied on the column that causes the failure.
- So we can conclude based on the above observations that this kind of the failure is not possible to repair.
- We can apply a temporary fix as we can see in the above image like they have applied a wooden support in order to carry the load in that particular time.
- But we must construct a new column as soon as possible to avoid the damage.
- So we can conclude after this discussion that this failure is not possible to repair. We must construct a new column to avoid any damages.