Most of the structures in Sri Lanka are made of reinforced concrete and considerable numbers of them are old structures, in which deterioration of concrete and corrosion of steel have become problems. Despite these deteriorations which reduce the structural performances, reinforced concrete structures are subjected to an abrupt usage during service lives. Quite often, this includes changing floor usage (often increasing loads) and reusing abandoned structures. Also, both monumental as well as water retaining concrete structures which have long history of surviving should be assessed regularly to check safety against progressive weakening. Both cracking of exposed concrete surface and steel corrosion result in unpredictable behaviours of reinforced concrete members under loading and this may cause capacity reduction of reinforced concrete members as well as loss of serviceability requirements. But, it is very difficult to investigate effect of damages such as concrete cracking and steel corrosion (Especially loss of bond) to both non linear responses and load carrying capacities of RC members using in-situ testing. Since, the use of finite element technique is well accepted and advanced; use of this tool can save both time and money while giving us reliable results.