Response of RC structures to near-fault records

Near-fault ground motions have special characteristics that affect the response of structures. Their importance in earthquake design of civil structures was not fully realized until several failures occurred during the 1994 Northridge and 1995 Kobe earthquake events. The objective of this study is to investigate the effect of near fault earthquakes on the response of reinforced concrete structures. A new technique based on digital filters is proposed to identify the special characteristics of near-fault ground motion and also to separate the near-fault pulses form the geological noise. The proposed method shows when a smoothed near-fault record with the same pulse duration and PGV can substitute the complete near-fault record. The response of flexible structures when subjected to filtered near-fault records was very close to the response of the complete near-fault record while for stiff structure the response is highly dependent on the high frequency content of the near-fault record. This shows that velocity pulses dominate the inelastic response to near-fault records for flexible structures. For this type of structures, conventional code design methodologies do not satisfy the actual demands of near-fault records. It was found that the response of structures to near-fault ground motion is substantially different from the response to far-field earthquake records. It is concluded that codes should address the near-fault
motion explicitly in time history form and not by the implicit form of increasing the coordinates of the design response spectra.