Effect of infill panels on the seismic vulnerability of non-ductile reinforced concrete frames

Abstract

Infill panels can increase seismic performance of reinforced concrete, RC frames if it is uniformly distributed in plan and along the height of the structures. This study investigates the effect of infill panels in seismic vulnerability of low-ductile RC frames which is commonly constructed in low-to-medium seismicity countries like Malaysia. This type of structures is seismically vulnerable since it has insufficient strength and ductility to resist earthquake loads. Fragility curves are used in this study to assess the vulnerability level of fully infilled RC frames under different intensity and characteristic of earthquake loads. RC frames with three, six, and nine stories designed for gravity and lateral loads based on the common practices in Malaysia were modeled and analyzed using incremental dynamic analysis (IDA). 45 earthquake records were used and 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. Results show a significant improvement in the seismic performance of low ductile fully infilled RC frames compared to the bare frames. The probability of exceeding CP damage level for PGA of 0.2g (maximum PGA for East and West Malaysia) in fully infilled frames is less than 20%. This is 30% lower than bare RC frames. It can be concluded that infill panels increases seismic capacities of non-ductile RC frames if it is distributed fully in the structures. Unlike bare RC frames that need to be retrofitted, fully infilled RC frames satisfy the no-collapse requirement for maximum PGA stated in the national annex.