Identification of Cracks

1.What is the mode of failure or damage of the beams in the figure above? Would you characterize the case as damage or as a failure? Are the damages repairable? Elaborate.

a. Here the figures shows shear failure, it mostly happens in beams. Shear failures in beams are caused by the diagonal cracks near the support providing no shear reinforcement. Beams fail immediately upon formation of critical cracks in the high-shear region near the beam supports. This failure can be avoided by using stirrups at that region. It is non repairable. A beam with proper stirrups placed at the high shear region must be made to avoid this kind of failure

b. The figure shows damaged column due to insufficient curing. When concrete is not cured properly, its durability, strength and abrasive resistance are affected. Due to inadequate curing, concrete develops plastic shrinkage cracks, thermal cracks, along with a considerable loss in the strength of the surface layer. The damages are repairable with proper plastering.

c. The figure shows failure at the column beam junction , plastic hinge failure . This happens mainly during earthquakes. This failure can easily lead to building collapse. It is non repairable. 

2.

a. This failure in figure is due to compression failure . The axial stress on the column is more than that the allowed stress . Compression failure occurs when then concrete starts to fail or bulge. It is non repairable.

b. This failure in figure is due to buckling. It is because slender beams used as structural elements can buckle when compressed, which could lead to instability and mechanical failure. This occurs due poor reinforcement and poor strength of concrete. this is non repairable.

c. The failure in figure is due to weak column strong beam joint, due to this crushing happens. While building it should be taken care of strong column and weak beam. This is non repairable damage.This should be cared during the construction stage.