Influence of ground motion frequency content on the nonlinear response and seismic performance of RC moment frame structures

Abstract

Several parameters may affect the response of structures to seismic excitation. These include features of the structures, properties of imposed ground motion and geological specifications of building location. This research has been conducted to investigate the effects of the frequency content of earthquakes as an important property of ground motion on the seismic performance and nonlinear response of reinforced concrete moment frame (RCMF) structures. To this end, forty-two earthquake records have been selected from the stations on site classes A and B based on ASCE7-10. These input excitations have been classified into three groups based on PGA to PGV ratios namely: Low, Intermediate, and High frequency motions. Three RCMFs with 2, 6, and 10 stories have been designed according to ACI318-14 and ASCE7-10. Finally, utilizing OpenSEES platform, based on the FE method a numerical model has been built to perform incremental dynamic analysis (IDA). After interpreting the results of the IDA, fragility curves have been obtained as a function of PGA for pre-defined damage states. The results showed that the associated PGA with the median of the fragility curve is in ascending order Low, Intermediate and High frequency motions. Accordingly, it is concluded that in the same PGA level, Low frequency motions are more probable to reach a damage threshold than Intermediate and High frequency motions. Similarly, Intermediate frequency motions is more capable reaching the damage threshold in comparison to High frequency motions.