Reliability of Iranian Existing Residential Reinforced Concrete Structures in Seismic Events

Structures failure prevention plays a vital role in saving the lives of citizens. The Iranian Code of Practice for the seismic-resistant design of buildings, Standard No. 2800, is one of the most critical and influential Iranian codes that are revised and edited regularly. Hence, this question arises: how will these regulations affect structures’ performance in future events? In this study, the performance of structures designed based on the third and fourth editions of standard No. 2800 is evaluated in operational (OP), immediate occupancy (IO), life safety (LS), and collapse prevention (CP) performance levels. The performance of structures is evaluated via two probabilistic approaches. Structural nonlinear analysis uses incremental dynamic analysis based on conditional mean spectrum-compatible records. The evaluations are carried out on three, five, and eight floors (three and five spans) intermediate moment resisting reinforced concrete structures. The results show that the seismic performance of structures in the later edition has improved compared to the previous one. However, the structures of both editions are safe at performance levels of OP, IO, and LS with a confidence level greater than 99%; the confidence level of CP performance level decreases with increasing height of structures so that the reliability of the fourth edition 8-story structures and third edition 5-story and 8-story structures is less than 90%. Therefore, it seems necessary to consider CP performance levels in seismic evaluations.