Earthquake recurrence effect on the response reduction factor of steel moment frame

Abstract

In this study, the effect of earthquake recurrence on the response modification factor (R factor) has been investigated. The response reduction factor of structures is one of the most important parameters for reducing the design force caused by earthquakes. An earthquake recurrence is a phenomenon caused by the accumulation of energy in faults and their continuous rupture. Given the release of energy in the faults, it is clear that the occurrence of an earthquake does not occur only once. It will often be accompanied by foreshocks and aftershocks. In some cases, the peak ground acceleration (PGA) of these foreshocks or aftershocks is as large as the main earthquake. Therefore, it is expected that the behavior of buildings under these seismic repetitions will vary with the behavior of structures under an earthquake. In this paper, the seismic behavior of moderate steel moment frames with 5, 10, and 15 floors was investigated under seven seismograms with repeating quakes. The calculation was done by performing the incremental dynamic analysis (IDA) on the R factor of these frames. The results show that the designed frames with the R factor from the main earthquakes (regardless of seismic sequence), faced with the dominant phenomenon of the main earthquake and its aftershocks, do not meet the expected performance. In this case, with the proposed correction factor, the response modification factor was modified. It was observed that the designed frames with the modified R factor under seismic sequence provided the desired performance expectations.