In Structural Engineering, retrofitting, repair and strengthening of structure are most commonly used words. It is important to distinguish them and defined them for better understanding.
Retrofitting: Retrofitting is the bringing the structure back to its original strength after damage + further increase in its strength to make it more strong than before.
Repair: Repair is bringing back the structure to its original strength after damage.
Strengthening: Strengthening is increase in strength of structure which is not damaged.
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