Identification of Cracks

1. (a)AIM: To find the mode of failure or damages of the beam given in the figure. Also if the damages are                                   repairable or not.

         OBSERVATIONS FROM THE FIGURE 1.(a):

          i. Concrete crushed and the reinforcement is exposed.

          ii. Concrete spalled beyond the reinforcement which may be a sign of rupture.

          iii. Beam top portion looks safe because of the flange advantage from slab. So there are no cracks in top of the beam.

          iv. The crack develops from bottom to top means rebar yielding occurs in support bottom only.

         ANSWER:

          i. Its form of Flexural failure due to reversal of stress during earthquake.

          ii. During stress reversal, support top experiences Compression and bottom experiences Tension.

          iii. Top compression is managed by slab advantage. Bottom tension was not satisfied by the provided reinforcement.

          iv. Since the reinforcement got yielded, it can not be repaired.

1. (b)AIM: To find the mode of failure or damages of the beam-column given in the figure. Also if the damages                       are repairable or not.

        OBSERVATIONS FROM THE FIGURE 1.(b):

        i. Cracks along Beam-Column edge.

        ii. Cracks seem to have developed through the structure as it looks much wider.

        iii. Beam looks seperated from the column at joints.

        iv. Concrete is not severely crushed.

        ANSWER:

        i. Its beam pull out failure due to insufficient development length of reinforcement in joints.

        ii. During earthquake, the horizontal movement of structure makes this condition worse and detached the beam member

            from column.

        iii. Providing anchorage length between two existing concrete is very difficult. So it cannot be repairable.

1. (c)AIM: To find the mode of failure or damages of the beam-column given in the figure. Also if the damages                       are repairable or not.

        OBSERVATIONS FROM THE FIGURE 1.(c):

        i. Cracks are exactly at the joint of the Column-Beam.

        ii. Cracks in Beam developed through its entire width.

        iii. Slab also developed more cracks along beam width direction.

        ANSWER:

        i. Its aPlastic hinge failure.

        ii. The damage occured only in the joint zone first of all.

        iii. Cyclic lateral loading and stress reversal at the joints led to the damage.

        iv. 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.

        v. The joint can be strengthened.

2. (a)AIM: To find the mode of failure or damages of the column given in the figure. Also if the damages                           are repairable or not.

        OBSERVATIONS FROM THE FIGURE 2.(a):

        i.Concrete damaged at top of Column.

        ii. Concrete damaged all around the Column face.

        iii. Beams are safe.

        iv. The location of column looks at edge of the building.

        v. No walls are built along the column means it is probably at Ground floor, for parking vehicles movement access.

        ANSWER:

        i. Its a soft storey failure, technically plastic hinge formation.

        ii. Due to absence of infill walls at the Ground floor the plastic hinge forms at the top of ground storey columns during                lateral  movement.

        iii. Based on the development of crush of concrete, it can either be repairable or non-repairable.

2. (b)AIM: To find the mode of failure or damages of the column given in the figure. Also if the damages                          are repairable or not.

        OBSERVATIONS FROM THE FIGURE 2.(b):

         i.Concrete developed complete breakage diagonally.

         ii. Longitudinal reinforcements are intact.

         iii. Shear reinforcement spacing looks wider(which means probably lesser shear rebar provided).

        ANSWER:

         i. Its a pure Shear failure.

         ii. Inadequate shear reinforcement compels concrete takes all the shear stresses.

2. (c)AIM: To find the mode of failure or damages of the column given in the figure. Also if the damages                          are repairable or not.

        OBSERVATIONS FROM THE FIGURE 2.(c):

        i. Column failed completely.

        ii. Failure at top of column.

        iii. There are two slabs connected to the column. Probably one at mid height of the column.

        iv. The wooden piles might be a post failure support after column failed, providing temporary prop to avoid collapse of                the entire structure.

        ANSWER:

        i. Its a short column failure.

        ii. An additional slab or a Beam connected to a column in mid-height leads to this effect.

        iii. This leads to failure especially if the connection is unintentional and not accounted in design.

        iv. The failure given in the picture is not at all repairable.