Identification of Cracks

1) a) As i understand this is a concrete beam crack which occurs due to corossion or insufficient concrete cover. As the lower section of the beam is exposed to the environment so the lower or the side face of the beam faces these cracks and it can be said as bottom reinforcement crack along the length. If we talk about the forces acting on them then it could be flexural failure because its the first failure then shear and in some cases can also be occurrence of torsion stress. And yes this is reparable so this is a failure.

b) This can be a wall crack orelse also plaster failure it can be serious if more than 15mm but below that it can be covered by plaster this occurs due to fluctuations in temperature and humidity levels.And yes it is repairable so it is a failure.

c) Plastic hinge or joint failure this occurs between beam column joints these occurs due to lateral reactions of seismic loads resulting in irreparable damage in the structure if the intensity is higher and can lead to building collapse also said as flexure shear failure. And it depends upon how much is the intensity of the load if higher than can't be repairable orelse can stand the building but can't resolve the effect given to the structure.

2) a) This might be concrete failure according to me and yes conrete can never regain its strength but if the failure is little than we can cover it by doing plaster.

b) splitting crack occurs due to excessive compression load coming upon the structure this can longitudinally and can lead to structure failure. And yes this can't be reperable as because this is a damage.

c) column failure according to me where due to high compressive force concrete failed and steel tried to participate to bear the load but once the concrete failed completely it can't be repaired these column failure occurs due to compression failure or due to buckling failure. And this is a damage and can't be reperable.