Seismic performance of limited ductile frames including softening

A large portion of existing building stock in Australia has not been designed to seismic loading. Even most of the structures built now are still typically designed only for gravity loads or with irrational response modification factors leading to limited ductility. It is very important to assess the seismic performance of the limited ductile structures. Unlike steel structures which strain harden, reinforced concrete structures characteristically soften beyond the elastic, plastic phases. Therefore the softening phase has to be considered in the evaluation of seismic performance these structures. It is the intention of this paper to provide a method for assessing the ductility of a reinforced concrete frame by evaluating the structure softening slopes.