There could be many reasons for the noted failure, but assuming there have been no significant loading changes, the most likely cause would be long-term deterioration of the reinforcing steel.  You might look at corrosion/exfoliation of the rebar and its causes.  Check the soluble chloride levels in the concrete.  You didn't give the crack width, frequency or severity, but indicated some torsion in the columns.  This is unusual and you should consider immediate shoring for safety reasons.  Once this is done, you can investigate the probable cause of the failure with less timidity and with greater deliberation.

Although I am not familiar with the specifics of the situation, I do have some experience with repair of corrosion effected structural concrete members.  I the case that comes to mind, there was a wall in an arch rib structure that had been "eaten" away by fertilizer storage.  We laminated a new face (apx.8") to the existing wall.  I should also not that the repaired area contained four pilasters.  Hope this may be of some help.

....continued.
Selecting a repair method is not appropriate until the extent and cause of the damage is determined.  It could range from a full-depth mortar repair for minor conditions to rebar replacement and re-casting for the extreme.  In between could include epoxy injection or carbon fiber wrapping.  Combinations of these methods may also be necessary; however, again...determine the extent of damage and its probable cause before proceeding.  I have seen numerous repairs to concrete deterioration that were ineffectual for the long term, simply because the wrong approach was taken for the specific application.

Once you have decided on a method, make sure the contractor doing the work is experienced in that type of repair and that proper materials are used.  Repair of structural concrete deterioration and cracking requires a high level of craftsmanship and understanding of the problems.  As an example, improper epoxy injection can cause additional damage to the concrete, or if the extent and orientation of the crack are not understood, the injection might not be adequate and further deterioration may follow.

Good luck.

I AM NOT FAMILIAR WITH THE REPAIRS BUT ONE THING I SUGGEST IS THE TO NOTICE WEATHER THEASE CRACKS HAVE OUCCERD ON THE END COLOUMS NOR ON THE INTERNAL COLOUMS,SINCE IT IS A FRAMED STRUCTURE YOU MIGHT KNOW ABOUT THE IMPORTANCE OF END COLOUMS. SO CARE MUST BE TAKEN AS FAST AS POSSIBLE.

good luck
vivekbabu@mailcity.com

I worked on a project involving second floor of a cafeteria structure.  Baking and dispensing of food was done on first floor.  Water operations occurred on second floor.  The floor had extensive damage (including rebar corrosion, spalling, cracking, leaking of contaminated washwater, etc.)  Based on considerable research of ACI, PCA, etc. I concluded that conventional fixes will not do permanent repair.  Repairs included shot blasting floor and ceilings, application of cementatious products, epoxies, epoxy crack injection, rebar rust cleaning,  and "CATHODIC PROTECTION to insure the water trapped in concrete (which is impossible to remove completely) does not continue to cause internal damage.  These steps may not be applicable to your case, but may provide some answers.

Ron is right.
Unless you find the cracks and torsion causes, any kind of solution could become wrong.

You should check your building with alignment measurements.

I've  worked a lot in renovation and construction pathology and that is what I've learned.

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