Identification of Cracks

Ans 1(a): It can be seen in fig 1(a) that there is damage at the bottom of the end of the beam.

Reason: The reason of failure is plastic hinge formation at the end of the beam which is flexural failure. It generally happens in strong column weak beam design. It is desirable that this type of failure should occur in moderate or large earthqukes.

Conclusion : This damage is distributed in all storeys in this type of failure and there is large displacement at collapse instead of that occurs in weak column strong beam design. The kind of failure in not repairable generally.

Ans 1(b): It can be seen in fig1(b) that there are diagonal cracks at the beam column connection.

Reason : The reason of failure is plastic hinge formation at the beam column connection.

Conclusion : This kind of failure is shear failure in which diagonal or X-shape cracks are formed at the beam column connection. It is undesirable that this kind of failure occurs during earthquake. This kind of failure result in loss in strength, stiffness and even collapse.

Ans 1(c) :It can be seen in fig1(c) that there failure at the beam column connection.

Reason : The reason is plastic hinge formation at the beam column connection.

Conclusion : This kind of failure is shear failure occurs at the beam column connection. It is undesirable that this kind of failure occurs during earthquake. This kind of failure result in loss in strength, stiffness and even collapse.

Ans 2(a) : It can be seen from the fig2(a) that failure occurs at the top of the column.

Reason : The kind of failure is compression failure which occurs due to excess axial stress. In this case the column cannot withstand load from the beam and results in compression failure. The rebars are bending inside under the beam and the rebars away from the beam are bending outside.

Conclusion : This kind of failure is also not repairable.

Ans 2(b) : It can be seen from the fig2(b) that the failure occurs in the column.

Reason : This is a buckling failure due to slender column. Slender column means longer height with minimum cross section.

Conclusion : This kind of failure is not repairable.

Ans 2(c) : It can seen from the fig2(c) that the failure occurs at the top of the column.

Reason : The reason of this failure is plastic hinge formation at the top of the column during earthquake.

Conclusion : It is a kind of flexural failure. It is undesirable that plastic hinge form at the top of the column. it may lead to complete collapse of the building. It is not repairable.