Identification of Cracks

1)

a)observation

• concrete crushed and reinforcement is exposed
• concrete spelled beyond the reinforcement which may be sign rapture
• beam top portion looks safe beacause of flange advantage from the slab
• the cracks develops from bottom to top means rebar yeilding occures in support bottom

ANS:

• it forms flexural failure due reversal of stress during earthquake
• during stress reversal support top experiances compression bottom experiences tention
• top compression is managed by slab advantage bottom tensu=ion is not satisfied by provide reinforcement
• ssince the reinforce met got yeilded it can not be repaired

b)

observation

• cracks along beam ccolumn edge
• cracs seems to ave develop through the structure as it looks much wider
• bea m looks saperate from column at joint
• cocrete is not sarvly crushed

ANS:

• its beam pull out failure due to insufficient development length of reinforcement in joints
• during earth quake the horizontal movement of structure make this condition worse and detached the beam member from column
• providing anchorage length between two existing concrete is very difficult so not repairable

C)

Obeservation

• cracks are a exactly at the joint of column beams
• cracs in beam developed through its entire width
• slab also developed more cracs along the beam width direction

ANS

• its plastic hinge failure
• the damage occured only in the joint zone first of a
• cyclic lateral loading and strss reversal at the joint led the damage
• even the slab participate to its best handle the tension /9 sslab is severly cracked means it has undergone tension with is flange codition but unable to contron te damge
• the joint can be strengened

2)

a)

obeservation:

• concrete damaged at top of column
• concrete damaged all around column face
• beams are safe
• te location of column looks edge of the building
• no wllas are built alng the column means it is probably at ground floor for parking car movement access

ANS:

• Its soft story failure , technically plastic hinge formation
• due to absence of infill walls at ground floor the plastic honge dors at top of ground storey columns during lateral movement
• based on development of crus of concrete it can be either be repairable or non repairabe

b)

observation

• concrete develop complete brakage diagonally
• logitudinal reinforcement are intact
• shear reinforcement spacing looks are wider ( probably leser tan shear bar provided

ANS:

• ITS pure shear failure
• inadequate sear reinforcement comples concrete takes all the shear sterss

c)

obeseravation

• columns failed complitly
• failure at top of column
• there are two slabs connected to column probably one at mid height of te column
• the wooden piles might be post failure support column failed ,providing emporary prop to avoid collapse of the entire strcture

ANS:

• its sort column failure
• an additional slab or beam connected to a column in mid heigt leads to this effect
• this leads to failure specially if the connection is unitentional and not accounted in design
• the failurec given in te pitchure is not ataall repairable