Identification of Cracks

Identification of Cracks

Question 1:

a) b) c)

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

ANS:

A)

this cracks will be formed due to the flexural failure of beam,

Observation:

1. concrete crushed and the reinforcement is exposed
2. Concrete spalled beyond the reinforcement which may be sign of rupture
3. beam top potion look safe beacause of the flange advantage from slab
4. the crcks develops from bottom to top meance rebars yeilding occurs in support bottom only

Answer

1. its form of flexural failure due to reversal of stress during eartquake
2. During stress reversal support top expriences compresssion and bottom expriences tention
3. top compression is managed by slab advantage, bottom tension was not satisfied by the provide reinforcement
4. since the reinforcement got yeilding, it can not be repaired

B)

Observation

1. cracks along beam column edge
2. cracks seem to have develop through the structure as it look much wider
3. beam looks separate from the column at joint
4. concrete is not severaly crushed

Answer

1. its beam pull out failure due to insufficient development length of reinforcement in joints
2. During earthquake the horizontal moment of structure makes this condition worse and detached the beam member from column
3. providing anchorage length between two existing concrete is very difficult so not repairable

C)

Observation

1. cracks are exactly at the joint of column beam
2. cracks in beam developed through its entire width
3. slab also developed more cracks along the beam width direction

Answer

1. its plastic hinge failure
2. the damage occured only in the joint zone first of all
3. cyclic lateral loading and stress reversal at the joint led to the damage
4. eaven the slab participated to its best to handle the tension but unable to control the damage
5. the joint can be strengthened

Question 2:

a) b) c)

ANS.

A)

Observation

1. Concrete damaged at top of a column
2. concrete damaged all around the column face
3. beam are safe
4. the location of column look at edge of the building
5. no walls are built along the column means it is probably at ground floor for parking car movement access

Answer

1. its soft storey failure technically plastic hinge formation
2. due to absence of infill walls at the ground floor the plastic hingeforms at the top of ground storey column during lateral movement
3. based on the development of crush concrete it can either be repairable or Non repairable

B)

1. Observation
2. concrete develop complete breakage diagonally
3. longitidinal reinforcement are intact
4. shear reinforcement spacing looks wider (which means probably lesser shear rebar provided )

Answer

1. its a pure shear failure
2. inadequate shear reinforcement compels concrete takes all the shear stresses
3. not repairable

C)

Observation

1. column failed completely
2. failure at top of column
3. there are two slabs connected to the column probably one at mid height of the column
4. the wooden piles might be a past failure support after column failed providing temporary prop to avoid collapse of the entire structure

Answer

1. its short column failure
2. an additional slab or a beam connected to a column in mid height leads to this effect
3. this leads to failure especially if the connection is unitensional and not accounted in design
4. the failure gives in the picture is not at all repairable