Seismic fragility of low ductile reinforced concrete frame in malaysia

Abstract

Seismic vulnerability of low-ductile reinforced concrete (RC) frames which have not been designed for earthquake loads has been a concern for countries with low-to-medium seismicity like Malaysia. These types of structures represent the majority of existing buildings in Malaysia and their safety level is of interest for authorities to plan for their retrofit. This study is conducted to assess the vulnerability of low-ductile reinforced concrete frame in Malaysia when subjected earthquake records through the development of seismic fragility curves. Three types of structural models were designed for gravity and lateral loads based on the common practices in Malaysia which included RC frames with three, six, and nine stories. The structures were analyzed using incremental dynamic analysis (IDA). In addition, pushover analysis was used to determine inter-story drift demands. The earthquake records were divided into three groups based on their peak ground acceleration (PGA) to peak ground velocity (PGV) ratios. Three structural performance levels namely immediate occupancy (IO), life safety (LS), and collapse prevention (CP) were considered for the selected frames. The results showed that records with the low PGA/PGV ratios that represented far-field earthquakes imposed the highest level of damage to the low-ductile RC frames. It was observed that the probability of seismic induced damage increased as the height of structures increased. The three story RC frame showed brittle failure mechanism when subjected to employed earthquake records. The probability of exceeding CP level under far-field records and the PGA of 0.2g was more than 50% for three and nine story RC frames. It was concluded that three and nine stories RC frames constructed in the East Malaysia did not satisfy the no-collapse requirements and needed to be retrofitted.