Identification of Cracks
1.(a) observation:
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 advantage from slab
the crack develops from bottom to top means rebar yeilding occurs in support bottom only.
its form of flexural failure due to reversal of stress during earthquake
during stress reversal , support top experiences compression and bottom experiences tension
top compression is managed by slab advantage. bottom was not satisfied by the provided reinforcement
since the reinforcement got yeilded , it can not be repaired.
1.(b) observation:
cracks along beam -column edge
cracks seem to have developed through the structure as it looks much wider
beam looks separated from the column at the joints
concrete is not severely crushed
its beam pull out failure due to insufficient development length of reinforcement in joints.
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 difficult. so not repairable.
1.(c) obsetrvation:
cracks are exactly at the joint of column - beam
cracks in beam developed through its entire width
slab also developed more cracks along the beam width direction
its a platis hinge failure
the damage occured only in the joint zone first of all
cyclic lateral loading and stress reversal at the joints led to the damage
even 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 damage
the joint can be strengthened
2.(a) observation:
concrete damaged at the top of a column
concrete damaged all around the column face
beams are safe
location of column looks at the edge of the building
no walls are built along the column, means it is probably at the ground floor , for parking car movement access
its a soft storey failure. technically plastic hinge formatioin
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 obn the development of crush of concrete , it can either be repairable or not
2.(b) observation:
concrete developed complete breakage diagonally
longitudinal reinforcements are intact
shear reinforcement spacing looks wider( probably lesser shear rebar provided)
its pure shear failure
inadequate shear reinforcements compels concrete takes all the shear stress
2.(c) observation:
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 post failure support after column failed , providing temporary prop to avoid collapse of the entire structure
its a short column failure
an additional or beam connected to a column in mid height leads to its effect
this leads to failure especially if the connection is uni tentional and not accounted in design
the failure given in the picture is not at all repairable