A new damage index for reinforced concrete structures subjected to seismic loads

Reinforced concrete structures are likely to experience some damage when subjected to earthquake loading. Damage index is a well accepted way of expressing the extent of damage and is widely used by researchers. Last few decades have seen many concepts for calibrating an appropriate damage index being proposed. This paper presents a detailed review of available concepts by classifying those into two broad categories: non-cumulative and cumulative. Non-cumulative indices do not include the effects of cyclic loading, whilst the cumulative indices are rather more rational. It is however observed that most of the existing damage indices are unable to accurately describe the state of damage of reinforced concrete structures. An ideal damage index should vary within a scale of 0 to 1 with 0 being the state of elastic response whilst 1 should refer to collapse; most of the existing damage indices do not satisfy this criteria. A new damage index based on the hysteretic energy is proposed herein and its performance is compared against the widely accepted concept proposed by Park and Ang (1985) in the case of a column subjected to compulsive cyclic displacement at top. The proposal is still at preliminary stage but it meets the essential criteria for a damage index