Identification of Cracks
CHALLENGE-1:-
Cracks Identification:-
- Crack identification in structures by detecting changes in their dynamic behavior has been studied in the past, and various methods have been developed, enabling the calculation of crack location and depth along a beam.
- Most of these methods utilize the frequency changes caused by the crack.
- This sensor is used for easy and accurate detection of cracks developed on the surface of concrete structures due to deterioration.
- The sensor is bonded onto a concrete structure, and the optical fiber cable is connected to a visible light source.
Objectives of these Challenge:-
- Awareness of Structural failures.
- Distingishing Structural and Non - Structural failures.
- To know how to obsrve a structural issuse
- Understanding Seismic failures.
What is the mode of failure or damage of the beams in the figure above? Are the damages repairable? Elaborate
1-a).
Observations:-
- Concrete crushed and the reinforcement is exposed.
- Concrete spalled beyond the reinforcement which may be a sign of rupture.
- Beam top portion looks safe because of the flange advantages from slab.
- The cracks develops from bottom to top means rebar yielding occurs in support bottom only.
Mode of failure:-
- Its form of Flexural failure due to reversal of stress during earthquake.
- The flexural strength, known as modulus of rupture, bend strength, or fracture strength, is a material property, defined as the stress in a material just before it yields in a flexure test.
- The flexural strength represents the highest stress experienced within the material at its moment of rupture. It is measured in terms of stress.
- During Stress reversal, support top experiences compression and bottom experiences tension.
- Top compression is managed by slab advantage. Bottom tension was not satisfied by provided reinforcement.
- Since the reinforcement got yielded, it can not be repaired.
_____________________________________________________________________________________________________
1-b).
Observations:-
- Cracks along Beam-Column edge.
- Cracks seem to have developed through the structure as it looks wider.
- Beam looks seperated from the column at joints.
- Horizontal member is deattached from the vertical member.
- Concrete is not severely crushed but its cracked as shown in figure above.
Mode of failure:-
- Its beam pull out failure due to insufficient development length of reinforcement in Joints that is Anchorage of reinforcement is not sufficient.
- At the beam-column joint the reinforcement is not sufficient. Then the lateral movement cannot be satisfied. So, beams are ultimately detached from the vertical member.
- 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 very difficult.
- Atleast one is old concrete and other is new section then we can use any dowel kind of things and we can acheive the anchorage length. But, here the both the elements are existing concretes and acheiving the anchorage length between these two is difficult.
- That is providing anchorage length between concrete is very difficult. So not repairable.
_____________________________________________________________________________________________________
1-c).
Observations:-
- Cracks are exactly at the joint of Column-Beam.
- Cracks in Beam developed through its entire width. The cracks actually at the face of the beam. It has been developed on both sides.
- Slab also developed more cracks along the beam width direction. Some random cracks are developed in the slab area also.
Mode of failure:-
- It's a Plastic hinge failure.
- The damage occured only in the joint zone first of all.
- Cyclic lateral loading & stress reversal at the joints led to the damage.
- Even the slab participated to its best to handle the tension (Slab is severely cracked means it has undergone tension with its flange condition), But unable to control the damage.
- The joint can be strengthened.
_____________________________________________________________________________________________________
2-a).
Observations:-
- Concrete damaged at top of a column.
- Concrete damaged all around the column face. It's not a one face, the spalling of the concrete occurs all around the column.
- Beam are safe as shown.
- The location of column looks at edge of the building.
- No walls are built along the column means it is probably at ground floor, for parking car movement access.
Mode of failure:-
- It's a Soft storey failure, Technically Plastic hinge formation.
- Due to absence of infill walls at the ground floor, The plastic hinge forms at the Top of ground storey columns during Lateral movement.
- Based on the development of crush of concrete, it can either be repairable or non-repairable. Based on the severity of column that is concrete spalling.
_____________________________________________________________________________________________________
2-b).
Observations:-
- Concrete developed complete breakage diagonally.
- Longitudinal reinforcement are intact.
- Shear reinforcement spacing looks wider (which means probably lesser shear rebar provided).
Mode of failure:-
- It's a Pure Shear failure.
- Inadequate shear reinforcement compels concrete takes all the shear stresses.
_____________________________________________________________________________________________________
2-c).
Observations:-
- Column failed completely.
- Failure at top of column.
- There are two slabs connected to the column, Probably one at mid height of the column.
- The wooden piles might be a post failure support after column failed, providing temporary prop to avoid collapse of the entire structure.
Mode of failure:-
- It's a short column failure.
- An additional slab or a beam conneted to a column in mid-height leads to this effects.
- This leads to failure especially if the connection is unintentional and not accounted in design.
- The failure given in the picture is not at all repairable.
______________________________________________***THE END***__________________________________________