Seismic risk assessment for a reinforced concrete frame designed according to Chinese codes

The analytical formulations of two types of seismic fragility functions, namely seismic demand fragility and seismic damage fragility, are derived from the general definition of fragility function and usually adopted assumptions in seismic risk assessment. Using suitable intensity measure (IM) and damage measure (DM), the well-known Cornell's IM- and displacement-based formulations for seismic risk are revisited from the viewpoint of the analytical fragility functions. It is found that the recently widely used formulations using engineering demand parameters (EDPs) as well as DM-based approaches are two specific cases of the general IM-based risk equation, depending on the chosen fragility parameters. To apply Cornell's formulations to assess the seismic performance of Chinese code-conforming buildings and to investigate the effects of the derived fragility parameters on the seismic performance, a five-storey reinforced concrete (RC) frame designed according to the Chinese codes has been used as a case study. The results of this example study demonstrate that the capacity randomness and the selection of earthquake IMs all have obvious influences on seismic fragility and risk. It is also found that the computed failure probabilities for different limit states in 50 years for the example frame all satisfy the probabilistic safety requirements by the Chinese code for seismic design of reinforced concrete buildings.