OPTIMIZATION OF REDUNDANCY PROBLEMS IN RELIABILITY BY META-HEURISTIC METHODS HASATTRACTED ATTENTION OF MANY RESEARCHERS DURING THE LAST FEW YEARS. IN THIS PAPER, WEHAVE USED HIERARCHICAL MEMETIC ALGORITHM (HMA) TO OPTIMIZE THE MIXED REDUNDANCY OFA BRIDGE NETWORK UNDER COST CONSTRAINT IN MINIMAL PATHS TO INCREASE THE EFFICIENCY OF THERELIABILITY. WE HAVE APPLIED MIXED COLD AND HOT REDUNDANCIES FOR ALL LEVELS (COMPONENTS, SUBSYSTEMS AND SYSTEM) SIMULTANEOUSLY IN THE NETWORK. WHAT IS INTERESTING IN THISPAPER IS THAT THERE IS NO LIMITATION ON THE TYPE OF DISTRIBUTION OF EACH COMPONENT.THEREFORE, WE TRY TO OPTIMIZE MIXED REDUNDANCY FOR ALL THE LEVELS AND FIND THE MAXIMUMRELIABILITY FOR DIFFERENT COSTS IN A NETWORK. FINALLY, THE NUMERICAL RESULTS HAVE BEENDERIVED BY HMA.