How to solve column failure in a constructed structure?

If the the dimension and steel reinforcement of the column are adequate and the problem in the compressive strength of the column, it is usually recommended to inject the column with strengthening groute rather than complete removal and reconstruction  as SAMIH said because it is sometimes not applicable but if applicable his answer is sufficient.

If the failure is due to smaller dimension or lower steel reinforcement , the proping mentioned by SAMIH will be applied and caging technique will be used. The technique depends on dwelling an external extra steel cage creating a new column and then shutter the column with the new dimension and recast it.

CFRP and Column Jacketting.

IF THE COMPLETE STRUCTURE HAS NOT FAILED BY THE FAILURE OF COLUMN THEN WE SHALL GIVE PROPS FOR THE SUPPORTED STRUCTURE (SLAB)  ACCORDING TO THE LOADING CONDITION IMMEDIATELY.THEN DEMOLISH THE ENTIRE COLUMN AND RECAST IT WITH HIGH GRADE CONCRETE